WO2023162937A1 - Dispersion liquide de nanotubes de carbone, stratifié, méthode de production de dispersion liquide de nanotubes de carbone, et méthode de production de film de carbone - Google Patents

Dispersion liquide de nanotubes de carbone, stratifié, méthode de production de dispersion liquide de nanotubes de carbone, et méthode de production de film de carbone Download PDF

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WO2023162937A1
WO2023162937A1 PCT/JP2023/006082 JP2023006082W WO2023162937A1 WO 2023162937 A1 WO2023162937 A1 WO 2023162937A1 JP 2023006082 W JP2023006082 W JP 2023006082W WO 2023162937 A1 WO2023162937 A1 WO 2023162937A1
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carbon nanotube
nanotube dispersion
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carbon
dispersion
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Japanese (ja)
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智子 山岸
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日本ゼオン株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/74—Iron group metals
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • C01B32/164—Preparation involving continuous processes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C01B32/174—Derivatisation; Solubilisation; Dispersion in solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

Definitions

  • the present invention relates to a carbon nanotube dispersion, a laminate, a method for producing a carbon nanotube dispersion, and a method for producing a carbon film.
  • Secondary batteries such as lithium-ion secondary batteries are small, lightweight, have high energy density, and can be charged and discharged repeatedly, and are used in a wide range of applications. Therefore, in recent years, improvements in battery members such as electrodes have been studied for the purpose of further improving the performance of secondary batteries.
  • an electrode for a secondary battery such as a lithium ion secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector.
  • the electrode mixture layer is formed by binding the components such as the electrode active material and/or the component such as the electrode active material and the current collector with a binder.
  • an electrode mixture layer in which carbon nanotubes are dispersed as a conductive material is used.
  • the electrode mixture layer is formed from a slurry composition containing components of the electrode mixture layer, for example, by coating the slurry composition on a current collector and drying it. Then, the slurry composition is prepared by mixing an electrode active material, a carbon nanotube dispersion, a binder, and an additive such as a dispersant added as necessary, as described in Patent Document 1, for example. You can also
  • CNT carbon nanotubes
  • a carbon nanotube film (hereinafter referred to as “CNT film” or “carbon film”), which is sometimes referred to as “bucky paper”, in which multiple CNTs are aggregated in the form of a film. It is proposed to manufacture a CNT film and use the CNT film as a conductive sheet, a heat conductive sheet, an electromagnetic wave absorbing sheet, or the like.
  • CNT dispersion a solution in which CNTs are dispersed (CNT dispersion) is prepared, this solution is applied to a substrate or the like, and components other than CNTs are removed to obtain aggregates of CNTs contained in the CNT dispersion. is formed into a film to produce a carbon film.
  • a CNT dispersion for example, a solvent having a viscosity and density within a predetermined range and a carbon nanotube aggregate having a content within a predetermined range dispersed in the solvent are provided, and physical properties such as scale width and density are predetermined.
  • Patent Document 1 A carbon nanotube dispersion (Patent Document 1) characterized by being within the range, a CNT dispersion containing a solvent, CNTs exhibiting predetermined physical properties, and ion particles (Patent Document 2), and CNTs and a molecular weight of a predetermined value or less.
  • Patent Document 3 A CNT dispersion containing a surfactant and a solvent (Patent Document 3) and the like have been proposed.
  • Electrodes for secondary batteries such as lithium-ion secondary batteries have the form of a laminate of a current collector made of metal or the like and an electrode mixture layer. Such an electrode is required to have strong peel strength between the electrode mixture layer and the current collector in order to increase the mechanical strength.
  • Electrodes for secondary batteries such as lithium ion secondary batteries can also be produced by transferring a prefabricated electrode mixture layer onto a current collector.
  • an electrode mixture layer with a release substrate which has the form of a laminate of a substrate (release substrate) made of a resin or the like and an electrode mixture layer. (electrode mixture layer for transfer) can be used.
  • Such an electrode mixture layer with a peelable substrate is required to have weak peel strength between the electrode mixture layer and the peelable substrate in order to enhance the easy peelability of the peelable substrate.
  • secondary batteries such as lithium-ion secondary batteries are required to have excellent rate characteristics as battery performance.
  • the secondary battery electrode when the present invention is used to prepare an electrode mixture layer, the secondary battery electrode can exhibit strong peel strength between the electrode mixture layer and a current collector composed of a metal or the like. It is possible to allow the electrode mixture layer with the release base material to exhibit weak peel strength between the electrode mixture layer and the release base material composed of resin or the like, and to exhibit excellent rate characteristics in the secondary battery.
  • An object of the present invention is to provide a carbon nanotube dispersion that can Another object of the present invention is to provide a laminate that can be used as an electrode for a secondary battery, having a strong peel strength between the electrode mixture layer and a current collector made of metal or the like.
  • a further object of the present invention is to provide a laminate that can be used as an electrode mixture layer with a release base material, which has a weak peel strength between the electrode mixture layer and the release base material made of resin or the like.
  • an object of the present invention is to provide a CNT dispersion capable of achieving good film-forming properties when forming a carbon film using the CNT dispersion, and a method for producing the same.
  • Another object of the present invention is to provide a method for producing a carbon film with good film-forming properties using a CNT dispersion.
  • the inventor of the present invention has diligently studied in order to achieve the above purpose. Then, the present inventors found that, as an index of a dispersion liquid suitable for preparing a slurry composition, the fractal dimension when analyzing the scattering curve obtained by measuring by the ultra-small angle X-ray scattering method with the Beaucage model, We found that the area ratio of carbon nanotubes in an image obtained by imaging a liquid can be used, and that the fractal dimension suitable for a slurry and the area ratio of a CNT dispersion differ depending on the physical properties of CNTs.
  • the inventors of the present invention found that the area ratio of CNTs in an image obtained by imaging a CNT dispersion is an index of the degree of good film-forming properties when forming a carbon film using a CNT dispersion. found that it can be used.
  • the inventors have found that good film-forming properties can be achieved by forming a carbon film using a carbon nanotube dispersion having an area ratio of 70% or less, and completed the present invention.
  • the carbon nanotube dispersion of the present invention is a carbon nanotube dispersion containing carbon nanotubes and a solvent
  • the fractal dimension in the wave number range of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less when analyzing the scattering curve obtained by measurement by the ultra-small angle X-ray scattering method with the Beaucage model is 3 It is characterized by being in the range of 4 or less.
  • the secondary battery electrode can exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal or the like.
  • the electrode mixture layer with the release base material can exhibit weak peel strength between the electrode mixture layer and the release base material composed of resin or the like, and to exhibit excellent rate characteristics in the secondary battery. be able to.
  • the fractal dimension can be obtained by the method described later.
  • the carbon nanotube dispersion of the present invention is a carbon nanotube dispersion containing single-walled carbon nanotubes having a G/D ratio of 5 or less and a solvent, wherein the carbon nanotube dispersion has a concentration of 0.1 wt %.
  • the carbon nanotube dispersion is characterized in that the area ratio of carbon nanotubes in an image obtained by imaging the liquid is 55% or less.
  • the area ratio of the carbon nanotubes measured above is 55% or less, so that the electrode mixture layer and the secondary battery electrode are formed. It is possible to demonstrate strong peel strength between the current collector made of metal etc. A weak peel strength can be exhibited, and a secondary battery can exhibit excellent rate characteristics.
  • the G/D ratio and the area ratio can be determined by the methods described in Examples.
  • the secondary battery electrode can further exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal or the like. This allows the electrode mixture layer with the release base material to further demonstrate the weak peel strength between the electrode mixture layer and the release base material composed of resin or the like, which is an excellent rate for secondary batteries. It is possible to further exhibit the characteristics.
  • the number of carbon nanotubes having an aspect ratio (length/diameter) within a predetermined range can be determined by the method described in Examples.
  • the carbon nanotube dispersion of the present invention is a carbon nanotube dispersion containing single-walled carbon nanotubes having a G/D ratio of 10 or more and a solvent, wherein the carbon nanotube dispersion has a concentration of 0.1 wt %.
  • the carbon nanotube dispersion is characterized in that the area ratio of carbon nanotubes in an image obtained by imaging the liquid is 75% or more.
  • the area ratio of the carbon nanotubes measured above is 75% or more, so that the electrode mixture layer and the secondary battery electrode are formed. It is possible to demonstrate strong peel strength between the current collector made of metal etc. A weak peel strength can be exhibited, and a secondary battery can exhibit excellent rate characteristics.
  • the G/D ratio and the area ratio can be determined by the methods described in Examples.
  • the carbon nanotube dispersion of the present invention is a carbon nanotube dispersion containing carbon nanotubes and a solvent, and occupies an image obtained by imaging the carbon nanotube dispersion at a concentration of 0.1 wt %.
  • the carbon nanotube dispersion liquid has a carbon nanotube area ratio of 70% or less.
  • the area ratio of the carbon nanotubes in the image obtained by imaging the carbon nanotube dispersion is preferably 20% or more and 70% or less, and 55% or more and 70% or less. is more preferable. If a CNT dispersion having an area ratio measured above of 20% or more and 70% or less, preferably 55% or more and 70% or less, is used, it has a high porosity of, for example, 60% or more and 99% or less, which is useful for battery applications. It becomes possible to obtain a carbon film.
  • the porosity of the carbon film can be determined by the method described in Examples.
  • the carbon nanotube dispersion of the present invention further has a scattering curve obtained by measuring by an ultra-small angle X-ray scattering method, and analyzing it with a Beaucage model, 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less, the fractal dimension is in the range of 3 or more and 4 or less.
  • the secondary battery electrode can exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal or the like. It is possible to allow the electrode mixture layer with the release base material to exhibit weak peel strength between the electrode mixture layer and the release base material composed of resin or the like, and to exhibit excellent rate characteristics in the secondary battery. Alternatively, good film formability can be achieved during the formation of the base film.
  • the carbon nanotube dispersion of the present invention has a scattering curve obtained by ultra-small-angle X-ray scattering, which is 0.05 (1/ ⁇ ) to 0.01 (1/ ⁇ ) or less, the CNT persistence length is preferably 100 nm or more.
  • the secondary battery electrode can further exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal or the like. This allows the electrode mixture layer with the release base material to further demonstrate the weak peel strength between the electrode mixture layer and the release base material composed of resin or the like, resulting in excellent rate characteristics for secondary batteries. It is possible to make the film more effective, or it is possible to achieve good film-forming properties during the formation of the base film.
  • the CNT persistence length can be obtained by the method described later.
  • the solvent is preferably water, alcohol, or a mixture of water and alcohol.
  • water when water is used as such a solvent, when a carbon film made of a carbon nanotube dispersion using the water is used in a battery, the affinity between the carbon film and the electrolyte is good, and the battery performance is improved. can be planned.
  • alcohol when alcohol is used as such a solvent, a carbon film can be easily produced using the carbon nanotube dispersion.
  • the carbon nanotubes preferably satisfy at least one of the following conditions (1) to (3).
  • (1) A spectrum obtained by Fourier transform infrared spectroscopic analysis of a carbon nanotube dispersion obtained by dispersing a carbon nanotube aggregate so that the bundle length is 10 ⁇ m or more, the plasmon resonance of the carbon nanotube dispersion At least one peak exists in the wavenumber range of more than 300 cm ⁇ 1 to 2000 cm ⁇ 1 or less.
  • the laminate of the present invention includes a metal film having a surface tension of 400 [mN/m] or more and 2000 [mN/m] or less, and carbon nanotubes formed using any of the carbon nanotube dispersions described above. It is characterized by being a laminate with a film.
  • the laminate is formed by directly laminating the metal film and the carbon nanotube-containing film.
  • the surface tension of the metal film can be determined by the method described in Examples.
  • the laminate of the present invention is a carbon nanotube formed using a substrate having a surface tension of 20 [mN/m] or more and 50 [mN/m] or less and any of the carbon nanotube dispersions described above. It is characterized by being a laminate with a containing film.
  • the laminate is formed by directly laminating the metal film and the carbon nanotube-containing film. In such a laminate, since the surface tension of the base material is small, the peel strength between the carbon nanotube-containing film and the base material is weak, and the carbon nanotube-containing film and the base material are easily separated. form a peelable laminate.
  • Such a peelable laminate can be used as a laminate (electrode mixture layer with a peelable substrate) to which a carbon nanotube-containing film (electrode mixture layer) can be easily transferred.
  • the surface tension of the substrate can be determined by the method described in Examples.
  • the method for producing a carbon nanotube dispersion of the present invention comprises: a step of dispersing a mixture of carbon nanotubes and a solvent to obtain a carbon nanotube dispersion; a step of measuring the obtained carbon nanotube dispersion by an ultra-small angle X-ray scattering method;
  • the fractal dimension in the wave number range of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less when analyzing the scattering curve obtained by measurement by the ultra-small angle X-ray scattering method with the Beaucage model is 3 or more
  • the method for producing a carbon nanotube dispersion of the present invention includes: a step of dispersing a mixture of carbon nanotubes and a solvent to obtain a carbon nanotube dispersion; 0.001 (1/ ⁇ ) in the wavenumber range of 0.3 (1/ ⁇ ) or more, the fractal dimension is 3 or more and 4 or less, and the wavenumber range of 0.05 (1/ ⁇ ) or more and 0.01 (1/ ⁇ ) or less a step of evaluating the carbon nanotube dispersion as being appropriate when the condition 2 in which the CNT persistence length is in the range of 100 nm or more is satisfied, and evaluating the carbon nanotube dispersion as being inappropriate when the condition 2 is not satisfied; , is preferably included.
  • the electrode mixture layer and the current collector composed of metal or the like are added to the secondary battery electrode. It is possible to further exhibit strong peel strength between the layers, and to further exhibit weak peel strength between the electrode mixture layer and the release substrate composed of a resin or the like in the electrode mixture layer with the release substrate. It is possible to obtain a carbon nanotube dispersion that can further exhibit excellent rate characteristics in secondary batteries.
  • the method for producing a carbon nanotube dispersion of the present invention comprises: a step of dispersing a mixture of single-walled carbon nanotubes having a G/D ratio of 5 or less and a solvent to obtain a carbon nanotube dispersion; For the obtained carbon nanotube dispersion, a step of imaging the carbon nanotube dispersion at a concentration of 0.1 wt% to obtain an image; If the condition 3 that the area ratio of the carbon nanotubes in the acquired image is 55% or less is satisfied, the carbon nanotube dispersion is evaluated as appropriate, and if the condition 3 is not satisfied, the carbon nanotube dispersion a step of evaluating the characterized by comprising According to this production method, when a carbon nanotube dispersion is produced using single-walled carbon nanotubes having a G/D ratio of 5 or less as the carbon nanotubes, the area ratio of the carbon nanotubes measured above is 55% or less.
  • the secondary battery electrode can exhibit a strong peel strength between the electrode mixture layer and the current collector composed of metal or the like, and the electrode mixture layer with the peeling base material can exhibit a strong peel strength. It is possible to obtain a carbon nanotube dispersion that can exhibit weak peel strength between the material layer and the release base material composed of resin or the like, and that can exhibit excellent rate characteristics in the secondary battery.
  • the method for producing a carbon nanotube dispersion of the present invention includes: a step of dispersing a mixture of single-walled carbon nanotubes having a G/D ratio of 5 or less and a solvent to obtain a carbon nanotube dispersion; For the obtained carbon nanotube dispersion, a step of imaging the carbon nanotube dispersion at a concentration of 0.1 wt% to obtain an image; The area ratio of carbon nanotubes in the acquired image is 55% or less, and 5 or more and 100 or less carbon nanotubes with an aspect ratio of 10 or more are included per area corresponding to 26000 ⁇ m 2 in the image.
  • the method for producing a carbon nanotube dispersion of the present invention comprises: a step of dispersing a mixture of single-walled carbon nanotubes having a G/D ratio of 10 or more and a solvent to obtain a carbon nanotube dispersion; For the obtained carbon nanotube dispersion, a step of imaging the carbon nanotube dispersion at a concentration of 0.1 wt% to obtain an image; If the condition 5 that the area ratio of the carbon nanotubes in the acquired image is 75% or more is satisfied, the carbon nanotube dispersion is evaluated as appropriate, and if the condition 5 is not satisfied, the carbon nanotube dispersion a step of evaluating the characterized by comprising According to this production method, when a carbon nanotube dispersion is produced using single-walled carbon nanotubes having a G/D ratio of 10 or more as the carbon nanotubes, the area ratio of the carbon nanotubes measured above is 75% or more.
  • the secondary battery electrode can exhibit a strong peel strength between the electrode mixture layer and the current collector composed of a metal or the like, and the electrode mixture layer with the peeling base material can be used. It is possible to obtain a carbon nanotube dispersion that can exhibit weak peel strength between the material layer and the release base material composed of resin or the like, and that can exhibit excellent rate characteristics in the secondary battery.
  • the method for producing a carbon nanotube dispersion of the present invention comprises the following steps: a step of dispersing a mixture of carbon nanotubes and a solvent to obtain a carbon nanotube dispersion; a step of capturing an image by imaging the obtained carbon nanotube dispersion; If the area ratio of the carbon nanotubes in the acquired image satisfies the condition A, the carbon nanotube dispersion is evaluated as appropriate, and if the condition A is not satisfied, the carbon nanotube dispersion is evaluated as not appropriate. and including The condition A includes that the area ratio of the carbon nanotubes in an image obtained by imaging the carbon nanotube dispersion at a concentration of 0.1 wt% is 70% or less.
  • the use of the CNT dispersion liquid obtained by this production method makes it possible to achieve good film-forming properties when forming a carbon film.
  • the condition A preferably further includes that the area ratio is 20% or more, more preferably 55% or more. If the CNT dispersion obtained by this production method is used under the condition that the area ratio of the carbon nanotubes measured above is 20% or more and 70% or less, preferably 55% or more and 70% or less, it is useful for battery applications. It is possible to obtain a carbon film having a high porosity of, for example, 60% or more and 99% or less. In addition, by using the carbon nanotube dispersion produced by this production method, it is possible to achieve a high porosity of, for example, 60% or more and 99% or less, which is useful for battery applications. can be determined step by step.
  • the method for producing the carbon nanotube dispersions of embodiments B1, B2, and C comprises: a step of measuring the obtained carbon nanotube dispersion by an ultra-small angle X-ray scattering method;
  • the fractal dimension in the wave number range of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less when analyzing the scattering curve obtained by measurement by the ultra-small angle X-ray scattering method with the Beaucage model is 3 or more
  • this manufacturing method under the condition that the fractal dimension measured above is in the range of 3 or more and 4 or less, there is a It is possible to exhibit a strong peel strength of the peeling base material layer, and the weak peel strength between the electrode mixture layer and the peeling base material composed of resin or the like can be exhibited. It is
  • the method for producing the carbon nanotube dispersions of embodiments B1, B2, and C comprises: a step of measuring the obtained carbon nanotube dispersion by an ultra-small angle X-ray scattering method;
  • the fractal dimension in the wave number range of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less when analyzing the scattering curve obtained by measurement by the ultra-small angle X-ray scattering method with the Beaucage model is 3 or more 4 or less, and the CNT persistence length in the wavenumber range of 0.05 (1/ ⁇ ) or more and 0.01 (1/ ⁇ ) or less is 100 nm or more.
  • a step of evaluating that the carbon nanotube dispersion liquid is not proper when the liquid is evaluated as proper and the condition 2 is not satisfied; is preferably further included.
  • the secondary battery electrode by further adding the condition that the CNT persistence length measured above is 100 nm or more, the secondary battery electrode has an electrode mixture layer and a current collector composed of metal or the like. It is possible to further exhibit strong peel strength between the layers, and to further exhibit weak peel strength between the electrode mixture layer and the release substrate composed of a resin or the like in the electrode mixture layer with the release substrate. It is possible to obtain a carbon nanotube dispersion that can further exhibit excellent rate characteristics in secondary batteries, or that can achieve good film-forming properties when forming a bare film.
  • the method for producing a carbon film of the present invention includes a step of forming a carbon film by removing the solvent from the above-described CNT dispersion having a CNT area ratio of 70% or less. According to this production method, by using a CNT dispersion having a CNT area ratio of 70% or less, a carbon film can be obtained with good film-forming properties.
  • the solvent is removed from the CNT dispersion obtained by the above-described method for producing a CNT dispersion and screened under the condition that the CNT area ratio is 70% or less, and the carbon film is obtained. including the step of forming a film.
  • this production method by using a CNT dispersion selected under the condition that the CNT area ratio is 70% or less, it is possible to obtain a carbon film with good film-forming properties.
  • the secondary battery electrode can exhibit a strong peel strength between the electrode mixture layer and the current collector composed of a metal or the like, and the electrode mixture layer with the peeling base material can It is possible to provide a carbon nanotube dispersion liquid that can exhibit weak peel strength between a composite material layer and a release base material composed of a resin or the like and that can exhibit excellent rate characteristics in a secondary battery. can. Further, according to the present invention, it is possible to provide a laminate that can be used as an electrode for a secondary battery, having a strong peel strength between the electrode mixture layer and the current collector made of metal or the like.
  • a laminate that can be used as an electrode mixture layer with a release base material, which has a weak peel strength between the electrode mixture layer and the release base material made of resin or the like. can be done.
  • a CNT dispersion capable of achieving good film-forming properties when forming a carbon film using the CNT dispersion, and a method for producing the same.
  • a method for producing a carbon film with good film-forming properties using a CNT dispersion it is possible to provide a method for producing a carbon film with good film-forming properties using a CNT dispersion.
  • FIG. 1 shows an optical microscope image of the CNT dispersion of Example 1.
  • FIG. 2 shows an optical microscope image of the CNT dispersion of Example 2.
  • FIG. 3 shows an optical microscope image of the CNT dispersion of Example 3.
  • FIG. 4 shows an optical microscope image of the CNT dispersion of Comparative Example 1.
  • FIG. 2 shows an SEM image of a CNT aggregate according to one example of CNTs used in the CNT dispersion of the present invention;
  • FIG. 2 shows a graph obtained by fitting the ultra-small angle X-ray scattering profiles of the CNT dispersions of Example 1 and Comparative Example 1 to the Beaucage equation. Schematic configuration of a CNT production apparatus used in Examples 1, 3 to 7 and Comparative Examples 1, 3, and 4 is shown.
  • FIG. 9 shows an image after binarization processing of the optical microscope image of FIG. 8.
  • FIG. 4 shows an image of the CNT dispersion of Example 1 after binarization.
  • 4 shows an image of the CNT dispersion of Example 2 after binarization.
  • 4 shows an image of the CNT dispersion of Example 3 after binarization.
  • a solid line indicates a carbon nanotube with an aspect ratio of 10 or more.
  • 4 shows an image of the CNT dispersion of Comparative Example 1 after binarization.
  • 4 shows an image of the CNT dispersion liquid of Comparative Example 2 after binarization processing.
  • the carbon nanotube dispersion of the present invention is a carbon nanotube dispersion containing carbon nanotubes and a solvent, and the scattering curve obtained by measurement by the ultra-small angle X-ray scattering method is analyzed by the Beaucage model.
  • the carbon nanotube dispersion liquid has a fractal dimension of 3 or more and 4 or less in the wave number range of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less.
  • the fractal dimension measured above is in the range of 3 or more and 4 or less, when used to form an electrode mixture layer, a current collector composed of an electrode mixture layer and a metal or the like in a secondary battery electrode It is possible to exhibit a strong peel strength between and the electrode mixture layer with the peeling base material can exhibit a weak peel strength between the electrode mixture layer and the peeling base material composed of resin or the like. , the secondary battery can exhibit excellent rate characteristics.
  • the carbon nanotube dispersion of the present invention is a carbon nanotube dispersion containing single-walled carbon nanotubes having a G/D ratio of 5 or less and a solvent, wherein the carbon nanotube dispersion has a concentration of 0.1 wt %.
  • a carbon nanotube dispersion liquid in which the area ratio of carbon nanotubes in an image obtained by imaging the liquid is 55% or less.
  • the area ratio of the carbon nanotubes measured above is 55% or less, so that when used to form the electrode mixture layer , the electrode for secondary batteries can exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal, etc., and the electrode mixture layer and the resin It is possible to exhibit weak peel strength with the release base material composed of such as, and it is possible to exhibit excellent rate characteristics in the secondary battery.
  • single-walled carbon nanotubes with a G/D ratio of 5 or less are used as carbon nanotubes
  • five carbon nanotubes with an aspect ratio (length/diameter) of 10 or more are used per area corresponding to 26000 ⁇ m 2 in the image. It is preferable that the number of 100 or less is more than 100. Since the number of carbon nanotubes having an aspect ratio of 10 or more is within the above range, when used to form an electrode mixture layer, a current collector composed of an electrode mixture layer and a metal or the like is formed in a secondary battery electrode. It is possible to further demonstrate the strong peel strength between the electrode mixture layer with the peeling base material, and further demonstrate the weak peel strength between the electrode mixture layer and the peeling base material composed of resin etc. It is possible to further exhibit the excellent rate characteristics of the secondary battery.
  • the carbon nanotube dispersion of the present invention is a carbon nanotube dispersion containing single-walled carbon nanotubes having a G/D ratio of 10 or more and a solvent, wherein the carbon nanotube dispersion has a concentration of 0.1 wt %.
  • a carbon nanotube dispersion liquid in which the area ratio of carbon nanotubes in an image obtained by imaging the liquid is 75% or more.
  • the area ratio of the carbon nanotubes measured above is 75% or more, so that when used to form the electrode mixture layer , the electrode for secondary batteries can exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal, etc., and the electrode mixture layer and the resin It is possible to exhibit weak peel strength with the release base material composed of such as, and it is possible to exhibit excellent rate characteristics in the secondary battery.
  • the carbon nanotube dispersion of the present invention is a carbon nanotube dispersion containing carbon nanotubes and a solvent, and the area ratio of the carbon nanotubes in the image obtained by imaging the carbon nanotube dispersion is 70%.
  • the following is a carbon nanotube dispersion.
  • the area ratio of the carbon nanotubes measured above is 70% or less, it is possible to achieve good film-forming properties when forming a carbon film using the CNT dispersion.
  • the area ratio of the CNT dispersion can be determined by the method described in Examples, and the film-forming properties of the carbon film can be evaluated by the method described in Examples.
  • the above carbon nanotube dispersion by setting the area ratio of the carbon nanotubes in the image obtained by imaging the carbon nanotube dispersion to a predetermined range, when forming a carbon film using the CNT dispersion, It is possible to obtain a carbon film having a porosity within a desired range. For example, if a CNT dispersion having an area ratio measured above of 20% or more and 70% or less, preferably 55% or more and 70% or less, is used, a high porosity of 60% or more and 99% or less, which is useful for battery applications, can be used. can be obtained.
  • the correlation between the area ratio of the CNT dispersion and the porosity of the obtained carbon film depends on the type of CNT, but in general, the higher the area ratio, the higher the porosity.
  • the porosity tends to decrease as the area ratio decreases.
  • a CNT dispersion prepared using CNT aggregates that satisfy at least one of the following conditions (1) to (3) is used.
  • At least one peak in the two-dimensional spatial frequency spectrum of the electron microscope image of the aggregate of carbon nanotubes exists in the range of 1 ⁇ m ⁇ 1 to 100 ⁇ m ⁇ 1 . If a more rigorous correlation between area ratio and porosity is required, a calibration curve showing the correlation between area ratio and porosity can be created for each type of CNT. A guideline for the area ratio that can achieve the desired porosity can be obtained.
  • the porosity of the carbon film can be determined by the method described in Examples.
  • the carbon nanotube dispersion of the present invention further has a scattering curve obtained by measuring by an ultra-small angle X-ray scattering method, and analyzing it with a Beaucage model, 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less, the fractal dimension is in the range of 3 or more and 4 or less.
  • the secondary battery electrode can exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal or the like. It is possible to allow the electrode mixture layer with the release base material to exhibit weak peel strength between the electrode mixture layer and the release base material composed of resin or the like, and to exhibit excellent rate characteristics in the secondary battery. Alternatively, good film formability can be achieved during the formation of the base film.
  • the scattering curve obtained by measuring the carbon nanotube dispersion of the present invention by the ultra-small angle X-ray scattering method was analyzed by the Beaucage model, and the scattering curve was 0.05 (1/ ⁇ ) to 0.01 (1/ ⁇ ) or less
  • the CNT persistence length is preferably 100 nm or more. Since the CNT persistence length measured above is 100 nm or more, when used to form the electrode mixture layer, the electrode mixture layer and the current collector composed of metal or the like are formed in the secondary battery electrode. It is possible to further exhibit strong peel strength between the layers, and to further exhibit weak peel strength between the electrode mixture layer and the release substrate composed of a resin or the like in the electrode mixture layer with the release substrate. It is possible to make the secondary battery more exhibit excellent rate characteristics, or to achieve good film-forming properties during the formation of the base film.
  • Carbon nanotubes (CNT) used in the carbon nanotube dispersion of the present invention are not particularly limited, but for example, it is preferable to use single-walled carbon nanotubes (single-walled CNTs). Single-walled carbon nanotubes (single-walled CNTs) are used. By using single-walled CNTs, a highly conductive CNT dispersion can be produced. Examples of CNTs include those that satisfy the conditions described below or are obtained by the manufacturing methods described below. In addition, the ratio of CNTs satisfying the conditions shown below or obtained by the production method shown below in the total mass of CNTs is preferably more than 50% by mass, more preferably 90% by mass or more. , more preferably 95% by mass or more, and may be 100% by mass.
  • the carbon nanotubes (CNT) used in the carbon nanotube dispersion of the present invention are not particularly limited, and single-walled carbon nanotubes and/or multi-walled carbon nanotubes can be used. is preferably contained as a main component.
  • Components other than single-walled CNTs that can be contained in CNTs include multi-walled carbon nanotubes (multi-walled CNTs).
  • the ratio of single-walled CNTs to the total mass of CNTs may be, for example, more than 50% by mass, preferably 90% by mass or more, more preferably 95% by mass or more, and 100% by mass. % may be used.
  • the number of layers of the multi-layered CNTs is preferably 5 or less.
  • a CNT dispersion with higher conductivity or a CNT dispersion that can produce self-sustaining carbon films with higher conductivity and porosity can be produced. can be made.
  • single-walled carbon nanotubes with a G/D ratio of 5 or less are used as CNTs.
  • the G/D ratio of CNTs is preferably 1 or more, more preferably 1.1 or more.
  • the G/D ratio of CNT is 5 or less, preferably 4.9 or less. If the G/D ratio is equal to or less than the above upper limit, it is easy to form a CNT network. Conversely, in a CNT aggregate whose G/D ratio is less than the above lower limit, the crystallinity of the single-walled CNTs is low, it is conceivable that there is a large amount of dirt such as amorphous carbon, and the multi-walled CNTs are mixed in at a high rate.
  • single-walled carbon nanotubes with a G/D ratio of 10 or more are used as CNTs.
  • the G/D ratio of CNT is preferably 10 or more, more preferably 11 or more.
  • the G/D ratio of CNTs is preferably 100 or less, more preferably 60 or less. If the G/D ratio is equal to or higher than the above lower limit, high crystallinity and conductivity can be expected. Conversely, a CNT aggregate having a G/D ratio exceeding the above upper limit has high linearity, CNTs tend to form a bundle with few gaps, and the specific surface area may decrease.
  • the G/D ratio is an index commonly used to evaluate the quality of CNTs. Vibrational modes called G band (near 1600 cm ⁇ 1 ) and D band (near 1350 cm ⁇ 1 ) are observed in the Raman spectrum of CNTs measured by a Raman spectrometer.
  • the G band is a vibrational mode derived from the hexagonal lattice structure of graphite, which is the cylindrical surface of CNT
  • the D band is a vibrational mode derived from amorphous sites. Therefore, a CNT with a higher peak intensity ratio (G/D ratio) between the G band and the D band can be evaluated as having higher crystallinity (linearity).
  • the G/D ratio can be determined, for example, by the method described in Examples.
  • the G/D ratio of the CNT mixture should be within the above range.
  • CNTs can be produced using known CNT synthesis methods such as an arc discharge method, laser ablation method, and chemical vapor deposition method (CVD method), without being particularly limited.
  • CNTs are synthesized, for example, by supplying a raw material compound and a carrier gas onto a substrate having a catalyst layer for producing carbon nanotubes on the surface, and synthesizing CNTs by chemical vapor deposition (CVD).
  • CVD chemical vapor deposition
  • a method of dramatically improving the catalytic activity of the catalyst layer by allowing a trace amount of oxidizing agent (catalyst activating substance) to exist in the system (super-growth method; see International Publication No. 2006/011655). , can be efficiently manufactured.
  • the carbon nanotube obtained by the super growth method may be called "SGCNT.”
  • CNTs preferably show an upward convex shape in the t-plot obtained from the adsorption isotherm.
  • the growth of a nitrogen gas adsorption layer on a substance having pores on its surface is classified into the following processes (1) to (3). Then, the slope of the t-plot changes due to the following processes (1) to (3).
  • the t-plot showing an upwardly convex shape is located on a straight line passing through the origin in a region where the average thickness t of the nitrogen gas adsorption layer is small, whereas when t becomes large, the plot is on the straight line.
  • position shifted downward from A CNT having such a t-plot shape has a large ratio of internal specific surface area to the total specific surface area of the CNT, indicating that a large number of openings are formed in the CNT.
  • the secondary battery can exhibit excellent rate characteristics, or good film-forming properties can be achieved during the formation of the base film.
  • the inflection point of the t-plot of CNT is preferably in the range that satisfies 0.2 ⁇ t (nm) ⁇ 1.5, and is in the range of 0.45 ⁇ t (nm) ⁇ 1.5. is more preferable, and it is even more preferable to be in the range of 0.55 ⁇ t(nm) ⁇ 1.0.
  • CNTs having the inflection point of the t-plot within such a range are more difficult to agglomerate in the dispersion liquid when such CNTs are used to prepare the dispersion liquid.
  • the secondary battery electrode can exhibit a strong peel strength between the electrode mixture layer and a current collector composed of a metal or the like.
  • the electrode mixture layer with the substrate can exhibit weak peel strength between the electrode mixture layer and the release substrate composed of resin or the like, and the secondary battery can exhibit excellent rate characteristics. Alternatively, good film-forming properties can be achieved during the formation of the base film.
  • the "position of the inflection point" is the intersection of the approximate straight line A in the process (1) described above and the approximate straight line B in the process (3) described above.
  • the CNT preferably has a ratio (S2/S1) of the internal specific surface area S2 to the total specific surface area S1 obtained from the t-plot of 0.05 or more and 0.30 or less.
  • S2/S1 a ratio of the internal specific surface area S2 to the total specific surface area S1 obtained from the t-plot of 0.05 or more and 0.30 or less.
  • CNTs having a value of S2/S1 within this range are more difficult to agglomerate in the dispersion when a carbon nanotube dispersion is prepared using such CNTs.
  • a carbon nanotube dispersion excellent in stabilizing the CNT network in the dispersion can be obtained.
  • the total specific surface area S1 and internal specific surface area S2 of CNT can be obtained from the t-plot. Specifically, first, the total specific surface area S1 can be obtained from the slope of the approximate straight line in process (1), and the external specific surface area S3 can be obtained from the slope of the approximate straight line in process (3). By subtracting the external specific surface area S3 from the total specific surface area S1, the internal specific surface area S2 can be calculated.
  • the measurement of the adsorption isotherm of CNT, the creation of the t-plot, and the calculation of the total specific surface area S1 and the internal specific surface area S2 based on the analysis of the t-plot can be performed, for example, by a commercially available measurement device "BELSORP ( (registered trademark)-mini” (manufactured by Nippon Bell Co., Ltd.).
  • the CNT preferably has a BET specific surface area of 600 m 2 /g or more, more preferably 800 m 2 /g or more, preferably 2000 m 2 /g or less, and 1800 m 2 /g or less. It is more preferably 1600 m 2 /g or less. If the BET specific surface area is within the above range, a CNT dispersion with excellent dispersibility can be produced.
  • the "BET specific surface area” refers to the nitrogen adsorption specific surface area measured using the BET (Brunauer-Emmett-Teller) method.
  • the average diameter of CNTs is preferably 1 nm or more, preferably 60 nm or less, more preferably 30 nm or less, and even more preferably 10 nm or less.
  • the average length of the CNTs is preferably 10 ⁇ m or more, more preferably 50 ⁇ m or more, even more preferably 80 ⁇ m or more, preferably 600 ⁇ m or less, and preferably 500 ⁇ m or less. More preferably, it is 400 ⁇ m or less.
  • CNTs having an average diameter and/or average length within the above range are less likely to aggregate in the carbon nanotube dispersion when such CNTs are used to prepare a carbon nanotube dispersion, resulting in a stabilized CNT dispersion. Liquid can be made.
  • Carbon nanotubes may be in the form of CNT aggregates.
  • CNTs in the form of CNT aggregates for example, CNT aggregates satisfying at least one of conditions (1) to (3) described later can be used.
  • a CNT dispersion liquid prepared using a CNT aggregate that satisfies at least one of the following conditions (1) to (3) has a strong peel strength when a laminate of a metal film and a carbon nanotube-containing film is formed. , weak peel strength when forming a laminate of a release substrate and a carbon nanotube-containing film, and excellent performance in terms of discharge rate characteristics when forming a secondary battery.
  • the CNT dispersion is suitable for obtaining carbon films with high porosity, since the carbon nanotubes have mesopores.
  • At least one peak in the two-dimensional spatial frequency spectrum of the electron microscope image of the aggregate of carbon nanotubes exists in the range of 1 ⁇ m ⁇ 1 to 100 ⁇ m ⁇ 1 .
  • FIG. 5 shows a scanning electron microscope (SEM) image of an example of a CNT aggregate that satisfies at least one of (1) to (3) above. As shown in FIG.
  • CNTs constituting a CNT aggregate that satisfies at least one of the above conditions (1) to (3) have a wavy structure. Due to such a "wavy structure", CNTs form a network structure. As a result, a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film, a weak peel strength when forming a laminate of a peeling substrate and a carbon nanotube-containing film, and a secondary battery are formed. It is speculated that this is reflected in the excellent performance of the discharge rate characteristics when the carbon nanotube has mesopores and is suitable for obtaining a carbon film having a high porosity.
  • Each of the above conditions (1) to (3) that can be satisfied by the CNT aggregate used for preparing the CNT dispersion of the present invention will be described in detail below.
  • the condition (1) is "a carbon nanotube dispersion obtained by dispersing aggregates of carbon nanotubes so that the bundle length is 10 ⁇ m or more.
  • the carbon nanotube dispersion At least one peak based on the plasmon resonance of is present in the wavenumber range of more than 300 cm ⁇ 1 and 2000 cm ⁇ 1 or less.
  • a strong absorption characteristic in the far-infrared region has been widely known as an optical characteristic of CNTs. Such strong absorption properties in the far-infrared region are believed to be due to the diameter and length of CNTs.
  • the wave number is in the range of more than 300 cm ⁇ 1 and 2000 cm ⁇ 1 or less, preferably in the wave number range of 500 cm ⁇ 1 or more and 2000 cm ⁇ 1 or less, more preferably in the wave number range of 700 cm ⁇ 1 or more and 2000 cm ⁇ 1 or less, If there is a peak based on the plasmon resonance of CNTs, a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film when using a CNT dispersion liquid using such CNTs, peeling substrate and a carbon nanotube-containing film when forming a laminate, and excellent performance in terms of discharge rate characteristics when forming a secondary battery. Moreover, since such CNTs have mesopores, a CNT dispersion using such CNTs is suitable for obtaining a carbon film having a high porosity.
  • the sharp peak near wavenumber 840 cm ⁇ 1 is attributed to CH out-of-plane bending vibration; the sharp peak near wavenumber 1300 cm ⁇ 1 is attributed to epoxy three-membered ring stretching vibration; wavenumber 1700 cm
  • T.M in the region of wave numbers exceeding 2000 cm ⁇ 1 , apart from the plasmon resonance, the above-mentioned T.M.
  • a peak similar to the S1 peak is detected. ⁇ 1 cm or less.
  • condition (1) in obtaining a spectrum by Fourier transform infrared spectroscopy, it is necessary to obtain a CNT dispersion by dispersing the CNT aggregates so that the bundle length is 10 ⁇ m or more.
  • a CNT aggregate, water, and a surfactant for example, sodium dodecylbenzenesulfonate
  • a surfactant for example, sodium dodecylbenzenesulfonate
  • the bundle length of the CNT dispersion can be obtained by analyzing it with a wet image analysis type particle size measuring device. Such a measuring device calculates the area of each dispersion from the image obtained by photographing the CNT dispersion, and the diameter of the circle having the calculated area (hereinafter also referred to as the ISO area diameter). ) can be obtained.
  • the bundle length of each dispersion is defined as the value of the ISO circle diameter thus obtained.
  • Condition (2) defines that "the maximum peak in the pore distribution curve is in the range of pore diameters greater than 100 nm and less than 400 nm.”
  • the pore size distribution of the aggregate of carbon nanotubes can be obtained from the adsorption isotherm of liquid nitrogen at 77K based on the BJH method.
  • the fact that the peak in the pore distribution curve obtained by measuring the carbon nanotube aggregate is in the range of more than 100 nm means that there are voids of a certain size between the CNTs in the carbon nanotube aggregate, and the CNTs are It means that it is not in an excessively densely agglomerated state.
  • the upper limit of 400 nm is the measurement limit when, for example, BELSORP-mini II is used as a measurement device.
  • a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film a weak peel strength when forming a laminate of a peeling substrate and a carbon nanotube-containing film, and forming a secondary battery From the viewpoint of further improving the performance of the discharge rate characteristics when the
  • the value of the log differential pore volume at the maximum peak of the pore distribution curve is preferably 2.0 cm 3 /g or more.
  • Condition (3) stipulates that "at least one peak in the two-dimensional spatial frequency spectrum of the electron microscope image of the aggregate of carbon nanotubes exists in the range of 1 ⁇ m -1 to 100 ⁇ m -1 ".
  • the sufficiency of such conditions can be determined in the following manner. First, the CNT aggregate to be determined is observed under magnification (e.g., 10,000 times) using an electron microscope (e.g., field emission scanning electron microscope), and a plurality of electron microscope images ( For example, 10 sheets) are obtained. A plurality of electron microscope images obtained are subjected to fast Fourier transform (FFT) processing to obtain a two-dimensional spatial frequency spectrum.
  • FFT fast Fourier transform
  • a two-dimensional spatial frequency spectrum obtained for each of a plurality of electron microscope images is binarized to obtain an average value of peak positions appearing on the highest frequency side.
  • the average value of the obtained peak positions was within the range of 1 ⁇ m ⁇ 1 or more and 100 ⁇ m ⁇ 1 or less, it was determined that the condition (3) was satisfied.
  • the "peak" used in the above determination a clear peak obtained by executing the isolated point extraction process (that is, the inverse operation of the isolated point removal) is used. Therefore, if a clear peak is not obtained within the range of 1 ⁇ m ⁇ 1 to 100 ⁇ m ⁇ 1 when the isolated point extraction process is performed, it is determined that the condition (3) is not satisfied.
  • a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film a weak peel strength when forming a laminate of a peeling substrate and a carbon nanotube-containing film, and forming a secondary battery Two-dimensional spatial frequency spectrum from the viewpoint of further improving the performance of the discharge rate characteristics when the is present in the range of 2.6 ⁇ m ⁇ 1 to 100 ⁇ m ⁇ 1 .
  • the CNT aggregates are At least two of the conditions (1) to (3) are preferably satisfied, and it is more preferable to satisfy all of the conditions (1) to (3).
  • the CNT aggregate that can be used to form the CNT dispersion of the present invention preferably has the following properties.
  • the CNT aggregate preferably has a total specific surface area by the BET method of 600 m 2 /g or more, more preferably 800 m 2 /g or more, preferably 2600 m 2 /g or less, more preferably 1400 m 2 /g or less. is. Furthermore, it is preferable that it is 1300 m ⁇ 2> /g or more in the thing which carried out the opening process.
  • the binding force between the CNT and the metal film is increased, and as a result, when a laminate of the metal film and the carbon nanotube-containing film is formed, a strong peel strength is obtained, and the peeling substrate and the carbon It is possible to further improve the weak peel strength when forming a laminate with a nanotube-containing film and the discharge rate characteristics when forming a secondary battery.
  • good film formability can be achieved when forming a carbon film using a CNT dispersion.
  • the CNT aggregate is mainly composed of single-walled CNTs and may contain double-walled CNTs and multi-walled CNTs to the extent that the functions are not impaired.
  • the total specific surface area of CNTs measured by the BET method can be measured using, for example, a BET specific surface area measuring device conforming to JIS Z8830.
  • the tap bulk density of the CNT aggregate is preferably 0.001 g/cm 3 or more and 0.2 g/cm 3 or less.
  • a CNT aggregate having such a density range does not excessively strengthen the bonds between CNTs, so that it has excellent dispersibility and can be molded into various shapes. If the tapped bulk density of the CNT aggregate is 0.2 g/cm 3 or less, the bonds between the CNTs become weak, so that when the CNT aggregate is stirred in a solvent or the like, it becomes easy to uniformly disperse it. Further, when the tap bulk density of the CNT aggregate is 0.001 g/cm 3 or more, the integrity of the CNT aggregate is improved and handling is facilitated.
  • the tapped bulk density is the apparent bulk density in a state in which the powdery CNT aggregates are filled in a container, and then the gaps between the powder particles are reduced by tapping, vibration, or the like to close-pack.
  • the G/D ratio of the CNT aggregate is preferably 1 or more and 50 or less.
  • a CNT aggregate with a G/D ratio of less than 1 is considered to have low crystallinity of single-walled CNTs, a large amount of dirt such as amorphous carbon, and a large content of multi-walled CNTs.
  • CNT aggregates with a G/D ratio of more than 50 have high linearity, CNTs tend to form bundles with few gaps, and the specific surface area may decrease.
  • the G/D ratio is an index commonly used to evaluate the quality of CNTs.
  • G band Near 1600 cm ⁇ 1
  • D band Near 1350 cm ⁇ 1
  • G band Vibrational modes called G band (near 1600 cm ⁇ 1 ) and D band (near 1350 cm ⁇ 1 ) are observed in the Raman spectrum of CNTs measured by a Raman spectrometer.
  • the G band is a vibrational mode derived from the hexagonal lattice structure of graphite, which is the cylindrical surface of CNT
  • the D band is a vibrational mode derived from amorphous sites. Therefore, a CNT with a higher peak intensity ratio (G/D ratio) between the G band and the D band can be evaluated as having higher crystallinity (linearity).
  • the purity of the CNT aggregates is as high as possible.
  • the purity is the carbon purity, and is a value indicating what percentage of the mass of the CNT aggregate is composed of carbon.
  • the purity is less than 95% by mass, it will be difficult to obtain a specific surface area exceeding 1000 m 2 /g without the opening treatment.
  • the carbon purity is less than 95% by mass due to metal impurities, the metal impurities react with oxygen during the opening process, preventing the opening of the CNTs.
  • the purity of single-walled CNTs is preferably 95% by mass or more.
  • a predetermined CNT aggregate that satisfies at least one of the above conditions (1) to (3) has a purity of usually 98% by mass or more, preferably 99.9% by mass, even without purification treatment. It can be as above. Impurities are hardly mixed in the CNT aggregate, and various characteristics inherent to CNT can be fully exhibited.
  • the carbon purity of the CNT aggregate can be obtained from elemental analysis using fluorescent X-rays, thermogravimetric analysis (TGA), or the like.
  • a method for producing a CNT aggregate is not particularly limited, and production conditions can be adjusted according to desired properties.
  • the conditions during the growth of the CNT aggregate must satisfy all of the following (a) to (c). It is necessary to meet (a) The growth rate of the CNT aggregate is 5 ⁇ m/min or more. (b) The catalyst activation material concentration in the growth atmosphere of the CNT aggregate is 4% by volume or more. (c) An obstacle exists in the growth direction of the CNTs that make up the CNT aggregate during the growth of the CNT aggregate.
  • a CNT aggregate that satisfies at least one of the above conditions (1) to (3) can be efficiently produced by a production method that satisfies all of the above (a) to (c). Furthermore, in this production method, there is no particular limitation as long as the above conditions (a) to (c) are satisfied during the growth of the CNT aggregate, and known methods such as the fluidized bed method, the moving bed method and the fixed bed method are used.
  • a CNT synthesis process according to can be employed.
  • the fluidized bed method means a synthesis method for synthesizing CNTs while fluidizing a granular carrier supporting a catalyst for synthesizing CNTs (hereinafter also referred to as a granular catalyst carrier).
  • the moving bed method and the fixed bed method mean synthesis methods for synthesizing CNTs without fluidizing a carrier (particulate carrier or plate-shaped carrier) supporting a catalyst.
  • a production method that satisfies all of the above-described (a) to (c) includes a catalyst carrier forming step of forming a catalyst carrier, and a catalyst carrier obtained in the catalyst carrier forming step. It includes a CNT synthesis step of synthesizing CNTs and a recovery step of recovering the CNTs synthesized in the CNT synthesis step. Then, the step of forming a supported catalyst can be carried out according to a known wet or dry catalyst supporting method. Also, the recovery step can be carried out using a known separation and recovery device such as a classifier.
  • the condition (a) that "the growth rate of the aggregate of carbon nanotubes is 5 ⁇ m/min or more" is achieved by appropriately adjusting the concentration, temperature, etc. of the raw material gas serving as the carbon source in the CNT growth atmosphere. can meet.
  • the raw material gas serving as a carbon source is not particularly limited, and hydrocarbon gases such as methane, ethane, ethylene, propane, butane, pentane, hexane, heptane, propylene and acetylene; Gases of lower alcohols; as well as mixtures thereof can also be used.
  • this raw material gas may be diluted with an inert gas.
  • a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film while further improving the dispersibility of the resulting CNT aggregate and a strong peel strength when forming a laminate of the peeling substrate and the carbon nanotube-containing film
  • CNT The aggregate growth rate is preferably 10 ⁇ m/min or more. Note that the temperature can be adjusted, for example, in the range of 400° C. or higher and 1100° C. or lower.
  • the raw material gas serving as a carbon source contain ethylene.
  • ethylene By heating ethylene in a predetermined temperature range (700° C. or higher and 900° C. or lower), the decomposition reaction of ethylene is promoted, and when the decomposition gas comes into contact with the catalyst, CNTs can grow at high speed.
  • the thermal decomposition time is too long, the decomposition reaction of ethylene proceeds too much, causing deactivation of the catalyst and adhesion of carbon impurities to the CNT aggregates.
  • the thermal decomposition time is preferably in the range of 0.5 seconds to 10 seconds with respect to the ethylene concentration in the range of 0.1 volume % to 40 volume %. If the time is less than 0.5 seconds, the thermal decomposition of ethylene is insufficient, making it difficult to grow a CNT aggregate with a high specific surface area at high speed. If the time is longer than 10 seconds, the decomposition of ethylene proceeds too much to generate a large amount of carbon impurities, resulting in deactivation of the catalyst and deterioration of the quality of the CNT aggregate. Thermal decomposition time is calculated from the following formula.
  • thermodecomposition time (heating channel volume)/ ⁇ (source gas flow rate) x (273.15+T)/273.15 ⁇
  • the heated channel volume is the volume of the channel heated to a predetermined temperature T° C. through which the raw material gas passes before coming into contact with the catalyst, and the raw material gas flow rate is the flow rate at 0° C. and 1 atm.
  • the concentration of the catalyst activation material in the growth atmosphere of the carbon nanotube aggregate is 4% by volume or more.
  • the concentration of the catalyst activating substance in the growth atmosphere of the CNT aggregate is 5 volumes. % or more.
  • the catalyst activation material is not particularly limited, and water, oxygen, ozone, acid gases, nitrogen oxides, carbon monoxide and carbon dioxide, and other low-carbon oxygen-containing compounds; ethanol, methanol and other alcohols; tetrahydrofuran; ketones such as acetone; aldehydes; esters; and mixtures thereof.
  • carbon dioxide is preferred.
  • Substances containing both carbon and oxygen, such as carbon monoxide and alcohols, may function as both a raw material gas and a catalyst activating substance.
  • carbon monoxide acts as a catalyst activating substance when combined with a more reactive raw material gas such as ethylene, and acts as a raw material gas when combined with a catalyst activating substance that exhibits a large catalytic activation effect even in a small amount such as water. .
  • condition (c) can be satisfied.
  • the CNT synthesizing step is carried out by, for example, supplying gas from below to fluidize the particulate catalyst support while supplying raw material gas.
  • the raw material gas may be supplied while the particulate catalyst carrier is continuously conveyed by screw rotation.
  • a catalyst carrier has a carrier and a catalyst supported on the surface of the carrier, and the carrier is a portion forming a matrix structure for supporting the catalyst by adhering, fixing, forming a film, or forming it on the surface of the carrier.
  • the carrier alone may be used, or a carrier with an underlayer provided with an arbitrary underlayer for favorably supporting the catalyst on the surface of the carrier may be used.
  • the shape of the carrier is preferably particulate, and the volume average particle diameter of the carrier is preferably 1 mm or less, more preferably 0.7 mm or less, and further preferably 0.4 mm or less. Preferably, it is 0.05 mm or more.
  • the growing CNT bundle will be thin, which is advantageous for forming a wavy structure.
  • the apparent density of the particles is preferably 3.8 g/cm 3 or more, more preferably 5.8 g/cm 3 or more, and preferably 8 g/cm 3 or less. If the particle density is equal to or higher than the above lower limit, the force applied to the growing CNT bundle increases, which is advantageous for forming a wavy structure.
  • the material of the support is preferably a metal oxide containing at least one element selected from Al and Zr. Among them, zirconia beads containing Zr with a large amount of elements are particularly preferable.
  • examples of the method for supporting the catalyst on the surface of the particulate carrier include a method using a rotary drum coating apparatus equipped with a substantially cylindrical rotary drum. .
  • the solution containing the components that can constitute the underlayer is applied to the particulate carrier. It is sprayed onto the surface of the carrier and dried to arrange the underlayer on the surface of the carrier. According to such a method, the catalyst layer and the underlayer can be formed relatively easily and evenly.
  • the “formation step” for reducing the catalyst supported on the catalyst support is performed prior to the “growth step” performed so as to satisfy the above conditions (a) to (c).
  • a “cooling process” can be performed to cool the catalyst carrier on which the CNTs have grown.
  • the atmosphere containing the catalyst carrier is used as a reducing gas atmosphere, and at least one of the reducing gas atmosphere and the catalyst carrier is heated to reduce and atomize the catalyst supported on the catalyst carrier. do.
  • the temperature of the catalyst carrier or reducing gas atmosphere in the formation step is preferably 400° C. or higher and 1100° C. or lower.
  • the execution time of the formation process may be 3 minutes or more and 120 minutes or less.
  • the reducing gas for example, hydrogen gas, ammonia gas, water vapor, and mixed gas thereof can be used.
  • the reducing gas may be a mixed gas in which these gases are mixed with an inert gas such as helium gas, argon gas, or nitrogen gas.
  • the catalyst carrier on which the CNTs have grown is cooled in an inert gas environment.
  • the inert gas an inert gas similar to the inert gas that can be used in the growth process can be used.
  • the temperature of the catalyst carrier on which the CNTs have grown is preferably lowered to 400° C. or lower, more preferably 200° C. or lower.
  • the CNT aggregates before dispersion can be subjected to a dry pulverization treatment.
  • dry pulverization treatment means pulverization treatment in a state in which the object to be pulverized does not substantially contain a solvent (for example, a solid content concentration of 95% or more).
  • a pulverizing device that can be used for the dry pulverizing treatment is not particularly limited as long as it can apply a physical load to an aggregate of fine structures by stirring or the like.
  • a mixer with rotating blades can be used as such a device.
  • pulverization conditions are not particularly limited.
  • the rotational speed is preferably 500 rpm or more and 5000 rpm or less
  • the pulverization time is preferably 10 seconds or more and 20 minutes or less.
  • the solvent for the CNT dispersion (hereinafter sometimes simply referred to as "solvent”) is not particularly limited, and examples include water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t -Alcohols such as butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and amyl alcohol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, diethyl ether, dioxane, tetrahydrofuran, etc.
  • solvent is not particularly limited, and examples include water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t
  • amide-based polar organic solvents such as N,N-dimethylformamide and N-methylpyrrolidone (NMP)
  • aromatic hydrocarbons such as toluene, xylene, chlorobenzene, ortho-dichlorobenzene and para-dichlorobenzene.
  • NMP N,N-dimethylformamide and N-methylpyrrolidone
  • aromatic hydrocarbons such as toluene, xylene, chlorobenzene, ortho-dichlorobenzene and para-dichlorobenzene.
  • NMP NMP
  • water, alcohols, or a mixture thereof is preferably used as the solvent for the CNT dispersion, and water is more preferably used.
  • the affinity between the carbon film and the electrolyte is good, and the battery performance is improved. can be planned.
  • alcohol is used as such a solvent, a carbon film can be easily produced using the carbon nanotube dispersion.
  • the solvent for the CNT dispersion and the solvent for the slurry composition may be the same or different, but from the viewpoint of keeping the solvent composition constant throughout the manufacturing process of the slurry composition, they are preferably the same. .
  • the content of carbon nanotubes in the carbon nanotube dispersion is not particularly limited, but from the viewpoint of dispersibility, it is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and 0.2% by mass or more. More preferred. From the viewpoint of dispersibility, the content of carbon nanotubes in the carbon nanotube dispersion is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.0% by mass or less.
  • the carbon nanotube dispersion of the present invention is assumed to be mixed with an active material, components for secondary battery electrodes such as a binder, and optionally a dispersant to produce a slurry composition for secondary battery electrodes. and that contamination with other components may inhibit the stability of the dispersion state of the carbon nanotube dispersion, or it is used to form a carbon film by removing the solvent. From the viewpoint of minimizing the residual amount of impurities in the formed carbon film, it is preferable that the total content of components other than the carbon nanotube and the solvent (i.e., dispersant, active material, binder, etc.) is as low as possible. More preferably, it does not contain a dispersant.
  • the carbon nanotubes and the solvent account for the majority.
  • the total content of the carbon nanotubes and the solvent in the carbon nanotube dispersion of the present invention is preferably 90% by mass or more, more preferably 95% by mass or more. More preferably, the nanotube dispersion contains no components other than the carbon nanotubes and the solvent.
  • a carbon nanotube dispersion can be obtained by subjecting a mixture of carbon nanotubes and a solvent to dispersion treatment.
  • the dispersing process can be performed using known mixing equipment.
  • a mixing device for example, a mixing device that can obtain a cavitation effect such as an ultrasonic dispersing machine and a jet mill, a bead mill, a ball mill, a roll mill, a sand mill, a pigment dispersing machine, a crusher, a homogenizer, a planetary mixer and Examples include a dispersing device such as Filmix, which can obtain a crushing effect.
  • a mixing device capable of obtaining a cavitation effect for the dispersion treatment.
  • the shock waves generated by the bursting of the vacuum bubbles generated in the water are used for dispersion.
  • the CNTs can be better dispersed.
  • the resulting coarse dispersion may be irradiated with ultrasonic waves using the ultrasonic disperser.
  • the irradiation time may be appropriately set depending on the amount of CNTs, and is preferably 3 minutes or longer, more preferably 30 minutes or longer, preferably 5 hours or shorter, and more preferably 2 hours or shorter.
  • the output is preferably 20 W or more and 500 W or less, more preferably 100 W or more and 500 W or less, and the temperature is preferably 15° C. or more and 50° C. or less.
  • the number of times of treatment may be appropriately set depending on the amount of CNTs.
  • the pressure is preferably 20 MPa or more and 250 MPa or less
  • the temperature is preferably 15° C. or more and 50° C. or less.
  • the CNT dispersion liquid disperses the CNT aggregates by a method using a stirring blade, a method using ultrasonic waves, a method using shear force, or the like.
  • a dispersion medium by the known method of
  • preferable conditions for each dispersion method for obtaining the CNT dispersion of the present invention are as follows.
  • the CNTs are dispersed in the dispersion medium at a rotation speed of the stirring blade of 1500 rpm or more and 12500 rpm or less, more preferably 2000 rpm or more and 10000 rpm or less, for 1 minute or more and 120 minutes or less, more preferably. is preferably performed for 5 minutes or more and 100 minutes or less.
  • Dispersion using a stirring blade can be performed using a known dispersing device having a stirring blade.
  • the CNTs are preferably dispersed in the dispersion medium at a frequency of 50 kHz or more and 500 kHz or less, 1 minute or more and 120 minutes or less, more preferably 2 minutes or more and 100 minutes or less.
  • Dispersion using ultrasonic waves can be performed using a known ultrasonic disperser.
  • the method for dispersing CNTs in the solvent is not particularly limited, and a general dispersing method using a conventionally known dispersing device can be adopted.
  • a CNT dispersion having a desired range of area ratio for example, 70% or less, preferably 20% or more and 70% or less, more preferably 55% or more and 70% or less
  • a dispersion liquid by subjecting it to a dispersion treatment for obtaining a cavitation effect or a dispersion treatment for obtaining a pulverization effect, which will be described in detail below.
  • the CNTs may be pre-dispersed in the solvent using a stirrer or the like.
  • Dispersion treatment that provides a cavitation effect is a dispersion method that utilizes shock waves generated by the bursting of vacuum bubbles in water when high energy is applied to the liquid.
  • CNTs can be well dispersed.
  • dispersion processing that can obtain a cavitation effect
  • dispersion processing using ultrasonic waves dispersion processing using a jet mill
  • dispersion processing using high-shear stirring Only one of these distributed processes may be performed, or a plurality of distributed processes may be combined.
  • An ultrasonic homogenizer, a jet mill, and a high-shear agitator, for example, are suitably used for the dispersion treatment that provides the cavitation effect.
  • Conventionally known devices may be used for these devices.
  • the pre-dispersion liquid or the mixed liquid before dispersion may be irradiated with ultrasonic waves by the ultrasonic homogenizer.
  • the irradiation time may be appropriately set according to the concentration and degree of dispersion of the CNTs.
  • various conditions may be appropriately set according to the concentration and degree of dispersion of CNTs, but the number of treatments is preferably 1 to 100, for example.
  • the pressure is preferably 20 MPa to 250 MPa, and the temperature is preferably 15°C to 50°C.
  • a high-pressure wet jet mill is suitable as a jet mill dispersing device, and specifically, "Nanomaker (registered trademark)” (manufactured by Advanced Nano Technology), “Nanomizer” (manufactured by Nanomizer), and “NanoVita”. (manufactured by Yoshida Kikai Kogyo Co., Ltd.), “Nano Jet Pal (registered trademark)” (manufactured by Joko Co., Ltd.), and the like.
  • the pre-dispersion liquid or the mixed liquid before dispersion may be agitated and sheared by a high-shear agitator.
  • the operating time time during which the machine is rotating
  • the peripheral speed is preferably 20 m/s to 50 m/s
  • the temperature is preferably 15°C to 50°C.
  • high-shear agitators include "Ebara Milder” (manufactured by Ebara Corporation), “Cavitron” (manufactured by Eurotech), and "DRS2000" (manufactured by IKA).
  • CLM-0.8S manufactured by M Technic Co., Ltd.
  • agitator typified by “TK Homomixer” (manufactured by Tokushu Kika Kogyo Co., Ltd.); turbine-type agitator typified by “TK Filmix” (manufactured by Tokushu Kika Kogyo Co., Ltd.).
  • - Dispersion processing that can obtain crushing effect -
  • a shearing force is applied to the pre-dispersed liquid or the mixed liquid before dispersion to crush and disperse the CNTs.
  • the CNTs can be uniformly dispersed in the solvent while suppressing the generation of air bubbles.
  • the dispersion treatment that provides the crushing effect can, of course, uniformly disperse the CNTs, and is more effective in suppressing damage to the CNTs due to shock waves when the bubbles disappear, compared to the dispersion treatment that provides the above-described cavitation effect.
  • the back pressure can be applied by applying a load to the flow of the pre-dispersion liquid or the mixed liquid before dispersion, for example, by arranging a multi-stage pressure-down device downstream of the disperser.
  • a desired back pressure can be applied to the liquid or mixed liquid prior to dispersion.
  • the applied back pressure may be reduced to atmospheric pressure at once, but it is preferable to reduce the pressure in multiple stages. This is because the pressure reduction in multiple stages by the multistage pressure reduction device can suppress the generation of air bubbles in the dispersion liquid when the CNTs are finally released to the atmospheric pressure.
  • a dispersion processing apparatus equipped with a capillary channel is used, and a preliminary dispersion liquid is pumped into the capillary channel to apply a shearing force to the preliminary dispersion liquid.
  • a dispersion treatment for dispersing the fibrous carbon nanostructures in is preferred. If the fibrous carbon nanostructures are dispersed by pumping the preliminary dispersion liquid into the capillary channel and applying a shearing force to the preliminary dispersion liquid, the occurrence of damage to the fibrous carbon nanostructures can be suppressed and the fibers can be dispersed.
  • the carbon nanostructures can be well dispersed.
  • Dispersion processing that provides a pulverization effect can be carried out by appropriately controlling the dispersing conditions using such a dispersing system.
  • the measurement by the ultra-small angle X-ray scattering method in step (ii) can be performed as follows. A dispersion of carbon nanotubes is dropped onto a slide glass, and ultra-small angle X-ray scattering measurement is performed on the droplets of the dropped carbon nanotube dispersion to obtain a scattering image.
  • ultra-small angle X-ray scattering measurement is performed with wave number q: 0.0004 (1/ ⁇ ) to 0.3 (1/ ⁇ ), X-ray source: CuK ⁇ , X-ray tube voltage: 45 kV, tube current: 200 mA.
  • slit width 10 mm
  • scan step 0.0006 deg
  • scan range 0 to 0.5 deg
  • scan speed 0.034 deg/min
  • X-ray detector two-dimensional semiconductor detector. Then, a scattering profile is obtained with the wave number q on the horizontal axis and the scattering intensity I(q) on the vertical axis.
  • ⁇ Fitting of scattering profile> The analysis of the measurement data by the ultra-small angle X-ray scattering method in step (iii) and the suitability evaluation of the carbon nanotube dispersion liquid can be performed as follows. Fitting is performed on the above scattering profile using the Beaucage formula. Fitting of scattering profiles using Beaucage's equation is well known in the art, see, for example, G. Beaucage,J. Appl. Cryst. , 28, 717 (1995). Fitting can be performed by using, for example, Igor Pro 8 (manufactured by WaveMetrics) as analysis software.
  • the Beaucage formula represented by the following general formula (I) with a wavenumber range of 0.0004 (1/ ⁇ ) to 0.3 (1/ ⁇ ) Fitting is performed using
  • q is the wavenumber (1/ ⁇ )
  • I(q) is the scattering intensity at wavenumber q
  • Bkgd is the background
  • G i and B i are proportionality constants
  • P i is the fractal dimension at hierarchy i.
  • R g,i is the length of the structure at layer i
  • N is the number of layers.
  • the fractal dimension P i in each layer i can be obtained by fitting the scattering profile using the general formula (I).
  • the fractal dimension is in the range of 3 or more and 4 or less.
  • the scattering (R g,1 ) derived from the diameter of one CNT is 0.01 (1/ ⁇ ) In the wavenumber range of 0.1 (1/ ⁇ ) or less, (2) the scattering (R g,2 ) derived from the persistence length of one CNT is 0.0001 (1/ ⁇ ) or more and 0.01 (1/ ⁇ ) In the following wavenumber range, (3) CNT bundle-derived scattering (R g,3 ) is observed. Also, in the scattering profile, the surface roughness (P 3 ) of the CNT bundle can be analyzed from the slope between scattering (R g,2 ) and scattering (R g,3 ).
  • a carbon nanotube dispersion having a fractal dimension of 3 or more and 4 or less in the wavenumber range of has a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film, and a laminate of a peeling substrate and a carbon nanotube-containing film.
  • the CNTs contained in the carbon nanotube dispersion having a fractal dimension of 3 or more and 4 or less in the wave number range of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less are unbundled and a CNT network can be formed. It is assumed that there are For this reason, CNTs form a network when a carbon nanotube-containing film is formed, and as a result, the carbon nanotube dispersion of the present invention has a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film, It is presumed that excellent performance can be exhibited with respect to weak peel strength when forming a laminate of the release base material and the carbon nanotube-containing film and excellent discharge rate characteristics when forming a secondary battery.
  • the CNTs in the CNT dispersion are shortened, and when the carbon nanotube-containing film is formed, the network is not formed, a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film, a weak peel strength when forming a laminate of a peeling substrate and a carbon nanotube-containing film, and a secondary battery It is presumed that the performance of the discharge rate characteristics when forming is deteriorated.
  • FIG. 1 shows an optical microscope image of the CNT dispersion of Example 1.
  • FIG. 2 shows an optical microscope image of the CNT dispersion of Example 2.
  • FIG. 3 shows an optical microscope image of the CNT dispersion of Example 3.
  • FIG. 4 shows an optical microscope image of the CNT dispersion of Comparative Example 1.
  • FIGS. 1 to 3 in the CNT dispersions of Examples 1 to 3, which have a fractal dimension of 3 or more and 4 or less within a predetermined wavenumber range, the CNT bundles are unraveled, the CNTs spread, and a network structure is formed.
  • the CNT dispersion of Comparative Example 1 which has a fractal dimension of less than 3 within a predetermined wavenumber range, has a large number of bundles and does not have a network structure like those of Examples 1-3. do not have. Therefore, in the CNT dispersion of Comparative Example 1, a CNT network is not well formed when a carbon nanotube-containing film is formed. , weak peel strength when forming a laminate of a release substrate and a carbon nanotube-containing film, and inferior performance in terms of discharge rate characteristics when forming a secondary battery.
  • the fractal dimension P i in general formula (I) corresponds to the absolute value of the slope of the straight line portion of the graph obtained by fitting the scattering profile to the Beaucage equation.
  • FIG. 6 shows a graph obtained by fitting the ultra-small angle X-ray scattering profiles of the CNT dispersions of Example 1 and Comparative Example 1 to the Beaucage equation.
  • the slope of the linear portion in the wave number range of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less in Example 1 is 0.001 (1/ ⁇ ) or more in Comparative Example 1. It is smaller than the slope of the linear portion in the wavenumber range of 0.3 (1/ ⁇ ) or less. That is, in the graph of Comparative Example 1 shown in FIG. I know there is.
  • the CNT dispersion of the present invention has a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film, and a weak peel strength when forming a laminate of a peeling substrate and a carbon nanotube-containing film.
  • the above-mentioned fractal dimension is a wave number of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less In the range, it is 3 or more, preferably 3.1 or more, more preferably 3.2 or more, and 4 or less, preferably 3.9 or less, and 3.8 or less. is more preferable.
  • the fractal dimension is adjusted, for example, by adjusting the CNT dispersion conditions (dispersion strength, dispersion time, presence or absence of a dispersant, etc.) when preparing the above-described CNT dispersion, and by adjusting the CNT bundle described later. It can be controlled by controlling the length and the like. For example, when CNTs are dispersed using a stirring blade, the CNT bundle length can be changed by changing the rotation speed (rpm) and/or the dispersion time of the stirring blade and/or the shape of the stirring blade.
  • the CNT dispersion of the present invention has a strong peel strength when forming a laminate of a metal film and a carbon nanotube-containing film, and a weak peel strength when forming a laminate of a peeling substrate and a carbon nanotube-containing film.
  • the persistence length of CNTs in the wave number range of 0.05 (1/ ⁇ ) or more and 0.01 (1/ ⁇ ) or less is preferably 100 nm or more, more preferably 105 nm or more, and further preferably 110 nm or more. preferable.
  • the persistence length of CNTs in the wave number range of 0.05 (1/ ⁇ ) or more and 0.01 (1/ ⁇ ) or less is not particularly limited, the persistence length of CNTs is usually 1000 or less.
  • the persistence length of CNT can be obtained in the same manner as the fractal dimension described above. Specifically, as described above, a carbon nanotube dispersion is dropped onto a slide glass, and the droplet of the dropped carbon nanotube dispersion is subjected to ultra-small angle X-ray scattering measurement to obtain a scattering profile. Then, the obtained scattering profile is fitted to the Beaucage equation represented by general formula (I) as described above.
  • R g,2 in layer 2 can be the persistence length of the CNT.
  • the CNT persistence length R g,2 represents the persistence length of the CNT in stratum 2 .
  • the persistence length of the CNTs is determined by, for example, adjusting the CNT dispersion conditions (dispersion strength, dispersion time, presence or absence of a dispersant, etc.) when preparing the above-described CNT dispersion, which will be described later. It can be controlled by controlling the CNT bundle length or the like. For example, when CNTs are dispersed using a stirring blade, the CNT bundle length can be changed by changing the rotation speed (rpm) and/or the dispersion time of the stirring blade and/or the shape of the stirring blade.
  • the carbon nanotube dispersion of the present invention can be used for any application. Among them, it is preferably used for forming an electrode mixture layer of an electrode for a secondary battery.
  • the carbon nanotube dispersion of the present invention is, for example, mixed with other components (e.g., electrode active material, binder, etc.) to produce a slurry composition for secondary battery electrodes.
  • the slurry composition for a secondary battery electrode obtained in this way is obtained by forming a carbon nanotube-containing film (electrode mixture layer) on the metal film, so that a laminate (two secondary battery electrode).
  • the secondary battery electrode slurry composition obtained in this manner is obtained by forming a carbon nanotube-containing film (electrode mixture layer) on a base material such as a resin, thereby exfoliating the base material and the carbon nanotube-containing film. It can be used to produce a laminate (electrode mixture layer for transfer).
  • An electrode obtained from the slurry composition for a secondary battery electrode can be used for producing a secondary battery.
  • the secondary battery is preferably a nonaqueous secondary battery, more preferably a lithium ion secondary battery.
  • the electrodes include positive electrodes and negative electrodes, with positive electrodes being preferred.
  • the secondary battery electrode is most preferably a lithium ion secondary battery positive electrode.
  • the carbon nanotube dispersion of the present invention By using the carbon nanotube dispersion of the present invention, a strong peel strength (that is, the mechanical strength of the electrode) when forming a laminate of a metal film and a carbon nanotube-containing film, Excellent performance is obtained with respect to weak peel strength when forming a laminate (that is, easy peeling of the electrode in the transfer electrode mixture layer) and discharge rate characteristics when forming a secondary battery.
  • a strong peel strength that is, the mechanical strength of the electrode
  • excellent performance is obtained with respect to weak peel strength when forming a laminate (that is, easy peeling of the electrode in the transfer electrode mixture layer) and discharge rate characteristics when forming a secondary battery.
  • the carbon nanotubes in advance in the form of a dispersion it is possible to improve the consistency and reproducibility of the state of dispersion of the carbon nanotubes in the slurry composition and the carbon nanotube-containing film (electrode mixture layer). It is suitable for repetitive mass production on an industrial scale and production at a high yield rate of products
  • a slurry composition for a secondary battery electrode can be produced by mixing the carbon nanotube dispersion of the present invention with other components.
  • Other components include, for example, electrode active materials, binders, solvents for slurry compositions, dispersants, and the like. Mixing can be performed, for example, by stirring (hard kneading) with a rotation-revolution kneading mixer (planetary mixer).
  • the slurry composition thus obtained can be used to produce a laminate (used as a secondary battery electrode) of a metal film and a carbon nanotube-containing film.
  • Electrode active material is a material that transfers electrons in the electrodes (positive electrode, negative electrode) of a secondary battery.
  • Electrode active materials include positive electrode active materials and negative electrode active materials.
  • the electrode active material is not particularly limited, and known electrode active materials used in secondary batteries can be used.
  • the electrode active material that can be used for the production of the composite used for the electrode of a lithium-ion secondary battery as an example of a secondary battery is not particularly limited, and can occlude and release lithium. Electrode active materials obtained from the following substances are exemplified.
  • Positive electrode active material for lithium ion secondary batteries include, for example, transition metal oxides, transition metal sulfides, and lithium-containing composite metal oxides of lithium and transition metals.
  • transition metals include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.
  • positive electrode active materials include conductive polymer compounds such as polyacetylene and poly-p-phenylene.
  • transition metal oxides examples include MnO, MnO 2 , V 2 O 5 , V 6 O 13 , TiO 2 , Cu 2 V 2 O 3 , amorphous V 2 O—P 2 O 5 and MoO. 3 and the like.
  • transition metal sulfides include TiS 2 , TiS 3 , amorphous MoS 2 and FeS.
  • lithium-containing composite metal oxides examples include lithium-containing composite metal oxides having a layered structure, lithium-containing composite metal oxides having a spinel structure, lithium-containing composite metal oxides having an olivine structure, and the like. .
  • lithium-containing composite metal oxides having a layered structure examples include lithium-containing cobalt oxides (LiCoO 2 ), lithium-containing nickel oxides (LiNiO 2 ), lithium composite oxides of Co—Ni—Mn, Ni— Mn--Al lithium composite oxide, Ni--Co--Al lithium composite oxide, and the like.
  • lithium-containing composite metal oxide having a spinel structure for example, lithium manganate (LiMn 2 O 4 ) or Li [Mn 1.5 M 0.5 ] in which part of Mn is replaced with another transition metal O 4 (where M is Cr, Fe, Co, Ni, Cu, etc.) and the like.
  • lithium-containing composite metal oxides having an olivine structure examples include Li X MPO 4 (wherein M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba , Ti, Al, Si, B and Mo, and X represents a number satisfying 0 ⁇ X ⁇ 2.).
  • one type of the positive electrode active material described above may be used alone, or two or more types may be used in combination at an arbitrary ratio.
  • a negative electrode active material for a lithium ion secondary battery includes a negative electrode active material made of carbon.
  • the negative electrode active material made of carbon include natural graphite, artificial graphite, carbon black, etc. Among them, graphite such as artificial graphite and natural graphite is preferable, and natural graphite is particularly preferable.
  • the negative electrode active material is a negative electrode active material containing metal.
  • a negative electrode active material containing at least one selected from the group consisting of tin, silicon, germanium and lead is particularly preferred.
  • a negative electrode active material containing these elements can reduce the irreversible capacity.
  • negative electrode active materials containing metal negative electrode active materials containing silicon are particularly preferable. By using a negative electrode active material containing silicon, it is possible to increase the electrical capacity of a lithium ion secondary battery.
  • silicon-containing negative electrode active materials include silicon-containing compounds and metallic silicon.
  • Compounds containing silicon are compounds of silicon and other elements, and examples thereof include SiO, SiO 2 , SiO x (0.01 ⁇ x ⁇ 2), SiC, and SiOC. Among these, SiO x , SiOC and SiC are preferred.
  • SiO x is a compound that can be formed from at least one of SiO and SiO 2 and metallic silicon. This SiO x can be produced, for example, by heating a mixture of SiO 2 and metallic silicon to cool and deposit silicon monoxide gas produced.
  • one of the negative electrode active materials described above may be used alone, or two or more of them may be used in combination at an arbitrary ratio.
  • the electrode active material described above preferably has a median particle diameter (D50) of 0.001 ⁇ m or more and 100 ⁇ m or less, more preferably 0.01 ⁇ m or more and 50 ⁇ m or less, and further preferably 0.1 ⁇ m or more and 30 ⁇ m or less. preferable. If the center particle diameter of the electrode active material is 0.001 ⁇ m or more, a slurry composition can be formed together with the carbon nanotube dispersion of the present invention, and the electrode mixture layer can be satisfactorily formed using the slurry composition.
  • D50 median particle diameter
  • the binder is not particularly limited, and for example, polymer compounds such as acrylic polymers, fluoropolymers, diene polymers, and nitrile polymers can be used. These polymer compounds can be used singly or in combination.
  • the binder may be dissolved in the solvent, or may be dispersed in the form of particles without being dissolved in the solvent.
  • the fluorine-based polymer, diene-based polymer and nitrile-based polymer include, for example, fluorine-based polymers, diene-based polymers and nitrile-based polymers described in JP-A-2012-243476. can be used.
  • an acrylic polymer for example, an acrylate-based polymer described in International Publication No. 2016/152262 can be used.
  • Acrylic polymer is a polymer containing repeating units (polymerized units) obtained by polymerizing acrylate or methacrylate (hereinafter sometimes abbreviated as "(meth)acrylate") and derivatives thereof, specifically includes homopolymers of (meth)acrylates, copolymers of (meth)acrylates, and copolymers of (meth)acrylates with other monomers copolymerizable with the (meth)acrylates.
  • the (meth)acrylate includes acrylics such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, and 2-ethylhexyl acrylate.
  • acid alkyl esters acrylic acid alkoxyalkyl esters such as 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate; 2-(perfluorobutyl)ethyl acrylate, 2-(perfluoropentyl)ethyl acrylate and the like 2-(perfluoroalkyl)ethyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid Methacrylic acid alkyl esters such as lauryl, tridecyl methacrylate and stearyl methacrylate; 2-(perfluoroalkyl)ethyl methacrylates such as 2-(perfluorobutyl)ethyl methacrylate and 2-(per
  • Alkyl acrylates such as -butyl and 2-ethylhexyl acrylate; and alkoxyalkyl acrylates such as 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate are preferred.
  • the content of polymerized units derived from (meth)acrylate in the acrylic polymer is usually 40% by mass or more, preferably 50% by mass or more, and more preferably 60% by mass or more.
  • the upper limit of the content of polymerized units derived from (meth)acrylate in the acrylic polymer is usually 100% by mass or less, preferably 95% by mass or less.
  • the monomer copolymerizable with the (meth)acrylate includes unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid and fumaric acid; Carboxylic acid esters having two or more carbon-carbon double bonds; styrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, hydroxymethylstyrene, ⁇ -methylstyrene, divinylbenzene styrene-based monomers such as; acrylamide, methacrylamide, N-methylolacrylamide, amide-based monomers such as acrylamido-2-methylpropanesulfonic acid; ⁇ , ⁇ -unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; Olefins such as ethylene and propylene; Diene monomers such as butadiene and isoprene; Vinyl esters
  • styrene-based monomers amide-based monomers, and ⁇ , ⁇ -unsaturated nitrile compounds are preferred.
  • the content of polymerized units derived from the copolymerizable monomer in the acrylic polymer is usually 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less.
  • the amount of the binder contained in the slurry composition for secondary battery electrodes is not particularly limited, and is preferably 0.05 parts by mass or more, and 0.1 parts by mass or more per 100 parts by mass. more preferably 0.2 parts by mass or more, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less. If the amount of the binder is within the above range, it is possible to exhibit a strong peel strength between the electrode mixture layer and the current collector composed of a metal or the like when used as an electrode for a secondary battery. When an electrode mixture layer with a material is used, it is possible to exhibit a weak peel strength between the electrode mixture layer and the release base material composed of resin, etc., and when it is used as a secondary battery, it has excellent rate characteristics. can be demonstrated.
  • the solvent for the slurry composition is not particularly limited, but includes those exemplified as the solvent for the CNT dispersion. Among them, it is more preferable to use NMP as the solvent for the slurry composition.
  • the solvent for the slurry composition and the solvent for the CNT dispersion may be the same or different, but from the viewpoint of keeping the solvent composition constant throughout the manufacturing process of the slurry composition, they are preferably the same. .
  • a dispersant is an additive for improving the dispersibility of each component (CNT, electrode active material, binder, etc.) of the slurry composition.
  • the dispersant is not particularly limited. Molecules or natural macromolecules can be used.
  • a laminate of a metal film having a surface tension of 400 [mN/m] to 2000 [mN/m] and a carbon nanotube-containing film formed using the carbon nanotube dispersion of the present invention is provided. be done.
  • the surface tension of the metal film is large, a strong peel strength is imparted between the carbon nanotube-containing film and the metal film, and the adhesion between the carbon nanotube-containing film and the metal film is improved. , to form a contact laminate.
  • the adhesion type laminate can be used as a member in which a carbon nanotube-containing film and a metal film are integrated, for example, a secondary battery electrode, preferably a lithium ion secondary battery positive electrode. It corresponds to the composite material layer, and the metal film corresponds to the current collector.
  • the metal film is not particularly limited as long as it is made of a metal material that can be used as a current collector and has a surface tension within a predetermined range.
  • a material having electrical conductivity and electrochemical durability is used.
  • metal films include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum.
  • copper foil is particularly preferable as the metal film used as the current collector for the negative electrode.
  • Aluminum foil is particularly preferable as the metal film used as the positive electrode current collector.
  • one type of the above materials may be used alone, or two or more types may be used in combination at an arbitrary ratio.
  • the thickness of the metal film is preferably about 0.001 mm or more and 0.5 mm or less.
  • the surface tension of the metal film is 400 [mN/m] or more, preferably 430 [mN/m] or more, more preferably 450 [mN/m] or more. Moreover, the surface tension of the metal film is 2000 [mN/m] or less, preferably 1950 [mN/m] or less, and more preferably 1900 [mN/m] or less.
  • the carbon nanotube-containing film formed from the carbon nanotube dispersion of the present invention is used as the carbon nanotube-containing film, and the surface tension of the metal film is within this range, the carbon nanotube network in the carbon nanotube-containing film is improved. Since it is formed, a strong adhesive force with the carbon nanotube-containing film is obtained, making it possible to form a contact laminate. Surface tension can be measured, for example, by the method described in Examples.
  • the adhesion type laminate (e.g., secondary battery electrode) of the present invention includes, for example, a step of applying the slurry composition for a secondary battery electrode described above onto a metal film (application step), and and a step (drying step) of drying the slurry composition for a secondary battery electrode to form a carbon nanotube-containing film (electrode mixture layer) on the metal film.
  • the method for applying the slurry composition for a secondary battery electrode onto the metal film is not particularly limited, and a known method can be used. Specifically, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, or the like can be used as the coating method.
  • the slurry composition for secondary battery electrodes may be applied to only one surface of the metal film, or may be applied to both surfaces.
  • the thickness of the slurry film on the metal film after application and before drying can be appropriately set according to the thickness of the carbon nanotube-containing film obtained by drying.
  • the method for drying the slurry composition for secondary battery electrodes on the metal film is not particularly limited, and known methods can be used. A drying method by irradiation with an electron beam or the like can be mentioned. By drying the positive electrode slurry composition on the current collector in this manner, a carbon nanotube-containing film is formed on the metal film, and a laminate (adhesion laminate) of the metal film and the carbon nanotube-containing film is obtained. be able to. Such a laminate can be used as a secondary battery electrode including a current collector and an electrode mixture layer.
  • the carbon nanotube-containing film may be pressurized using a mold press or roll press.
  • the pressure treatment can improve the adhesion between the carbon nanotube-containing film and the metal film.
  • a laminate of a substrate having a surface tension of 20 [mN/m] to 50 [mN/m] and a carbon nanotube-containing film formed using the carbon nanotube dispersion of the present invention is provided.
  • Such a laminate uses a carbon nanotube-containing film formed from the carbon nanotube dispersion of the present invention as the carbon nanotube-containing film, the carbon nanotube-containing film maintains a CNT network well, and the base material Since the surface tension of is small, the peel strength between the carbon nanotube-containing film and the substrate is weakened, and a peelable laminate with easy peelability is formed between the carbon nanotube-containing film and the substrate. .
  • the peelable laminate can be used as a member component in which the carbon nanotube-containing film and the substrate can be peeled off from each other, such as a transfer electrode mixture layer, preferably a transfer lithium ion secondary battery positive electrode mixture layer. can.
  • a transfer electrode mixture layer preferably a transfer lithium ion secondary battery positive electrode mixture layer.
  • the carbon nanotube-containing film corresponds to the electrode mixture layer
  • the substrate corresponds to the release substrate.
  • the transfer electrode mixture layer is formed by transferring the electrode mixture layer obtained by peeling off the base material from the transfer electrode mixture layer to the current collector, or by transferring the electrode mixture layer side of the transfer electrode mixture layer to the current collector.
  • the substrate is not particularly limited as long as it has a surface tension within a predetermined range, but it is preferably composed of a material that can be used as a release substrate.
  • a resin can be used as a material for such a base material.
  • resins include plastics (polyethylene, polypropylene, polystyrene, ABS resin, methacrylic resin, polyvinyl chloride, polyamide, polyacetal, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyphenylene oxide, polyamideimide, polyether ether ketone , polyphenylene sulfide, polytetrafluoroethylene, phenolic resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, etc.), synthetic rubber (isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, poly isobutylene rubber, ethylene propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, urethane rubber, silicone rubber, etc.), and natural rubber. These may be used alone or in combination of two or more.
  • the surface tension of the substrate is 20 [mN/m] or more, preferably 21 [mN/m] or more, and more preferably 22 [mN/m] or more.
  • the surface tension of the release substrate is 50 [mN/m] or less, preferably 49 [mN/m] or less, more preferably 48 [mN/m] or less. If the surface tension of the substrate is within this range, weak adhesion with the carbon nanotube-containing film is obtained, allowing the formation of a peelable laminate. Surface tension can be measured, for example, by the method described in Examples.
  • the peelable laminate (e.g., transfer electrode mixture layer) of the present invention can be obtained, for example, by applying the slurry composition for a secondary battery electrode described above onto a substrate (application step), and and a step (drying step) of drying the applied slurry composition for a secondary battery electrode to form a carbon nanotube-containing film (electrode mixture layer) on the substrate.
  • application step a step of applying the slurry composition for a secondary battery electrode described above onto a substrate
  • a step drying step of drying the applied slurry composition for a secondary battery electrode to form a carbon nanotube-containing film (electrode mixture layer) on the substrate.
  • drying step drying the applied slurry composition for a secondary battery electrode to form a carbon nanotube-containing film (electrode mixture layer) on the substrate.
  • a secondary battery such as a lithium ion secondary battery includes a positive electrode, a negative electrode, an electrolytic solution, and a separator.
  • a secondary battery electrode manufactured using the carbon nanotube dispersion of the present invention includes a positive electrode, a negative electrode, Or it can be used as both, preferably as a positive electrode.
  • Such a secondary battery has excellent rate characteristics.
  • each member and a method for manufacturing a secondary battery will be exemplified by taking a lithium ion secondary battery as an example in the case of manufacturing a positive electrode for a lithium ion secondary battery using the carbon nanotube dispersion of the present invention.
  • a known negative electrode can be used as the negative electrode.
  • the negative electrode for example, a negative electrode made of a thin plate of metallic lithium or a negative electrode formed by forming a negative electrode mixture layer on a current collector can be used.
  • a metal material such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum can be used.
  • a layer containing a negative electrode active material and a binder can be used as the negative electrode mixture layer. Note that the binder is not particularly limited, and any known material can be used.
  • an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used.
  • a lithium salt is used as the supporting electrolyte.
  • lithium salts include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi. , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi and the like.
  • LiPF 6 , LiClO 4 and CF 3 SO 3 Li are preferable, and LiPF 6 is particularly preferable, because they are easily dissolved in a solvent and exhibit a high degree of dissociation.
  • one electrolyte may be used alone, or two or more electrolytes may be used in combination at an arbitrary ratio.
  • lithium ion conductivity tends to increase as a supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted depending on the type of supporting electrolyte.
  • the organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte.
  • Examples include dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), Carbonates such as butylene carbonate (BC) and ethyl methyl carbonate (EMC); esters such as n-propyl propionate (PP), ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran ; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; and the like are preferably used.
  • a mixture of these solvents may also be used.
  • carbonates are preferably used because they have a high dielectric constant and a wide stable potential region. Note that the concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate. Further, known additives can be added to the electrolytic solution.
  • the separator is not particularly limited, and for example, those described in JP-A-2012-204303 can be used. Among these, polyolefin-based ( A microporous membrane made of resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred.
  • a secondary battery such as a lithium ion secondary battery includes, for example, a positive electrode and a negative electrode, which are superimposed with a separator interposed therebetween. It can be produced by injecting an electrolytic solution into a battery container and sealing it. In order to prevent an increase in internal pressure of the secondary battery and the occurrence of overcharge/discharge, etc., a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, or the like may be provided as necessary.
  • the shape of the secondary battery may be, for example, coin-shaped, button-shaped, sheet-shaped, cylindrical, rectangular, or flat.
  • the present invention provides a method for producing a carbon nanotube dispersion.
  • the method for producing a carbon nanotube dispersion of the present invention includes the following steps: (Ai) a step of dispersing a mixture of carbon nanotubes and a solvent to obtain a carbon nanotube dispersion; (A-ii) a step of measuring the obtained carbon nanotube dispersion by an ultra-small angle X-ray scattering method; (A-iii) a fractal dimension of 3 or more and 4 in the wave number range of 0.001 to 0.3 (1/ ⁇ ) when analyzing the scattering curve obtained by measuring by the ultra-small angle X-ray scattering method with the Beaucage model; The carbon nanotube dispersion is evaluated as appropriate when the following condition 1 is satisfied, and A step of evaluating that the carbon nanotube dispersion liquid is not appropriate when the condition 1 is not satisfied.
  • the fractal dimension measured above is in the range of 3 or more and 4 or less, there is a It is possible to exhibit a strong peel strength of the peeling base material layer, and the weak peel strength between the electrode mixture layer and the peeling base material composed of resin etc. can be exhibited. It is possible to obtain a carbon nanotube dispersion capable of exhibiting excellent rate characteristics in batteries.
  • the proper evaluation condition for step (A-iii) is that the CNT persistence length in the wavenumber range of 0.05 to 0.01 (1/ ⁇ ) is 100 nm or more.
  • the step (A-iii) is a fractal in the wave number range of 0.001 to 0.3 (1/ ⁇ ) when analyzing the scattering curve obtained by measuring by the ultra-small angle X-ray scattering method with the Beaucage model
  • the dimension is in the range of 3 or more and 4 or less and the CNT persistence length in the wavenumber range of 0.05 to 0.01 (1/ ⁇ ) is in the range of 100 nm or more
  • the carbon nanotube dispersion is It is preferable to evaluate that the carbon nanotube dispersion liquid is not appropriate when it is evaluated as appropriate and the condition 2 is not satisfied.
  • the secondary battery electrode by further adding the condition that the CNT persistence length measured above is 100 nm or more, the secondary battery electrode has an electrode mixture layer and a current collector composed of metal or the like. It is possible to further exhibit strong peel strength between the layers, and to further exhibit weak peel strength between the electrode mixture layer and the release substrate composed of a resin or the like in the electrode mixture layer with the release substrate. It is possible to obtain a carbon nanotube dispersion liquid that can further exhibit excellent rate characteristics in secondary batteries.
  • the method for producing the carbon nanotube dispersion of the present invention may further include the following steps: (A-iv) further dispersing the carbon nanotube dispersion when the carbon nanotube dispersion is evaluated as inappropriate; (Av) performing steps (A-ii) and (A-iii) again to evaluate whether the carbon nanotube dispersion is appropriate; (A-vi) Optionally repeating steps (A-iv) and (A-v).
  • the carbon nanotubes used in the method for producing a carbon nanotube dispersion of the present invention, the solvent, and the various content ratios in the mixture subjected to the dispersion treatment are the same as those described above. can be used. Further, the details of the distributed processing in steps (Ai) and (A-iv) are as described above. Furthermore, the details of the ultra-small angle X-ray scattering measurement in step (A-iii) are as described above.
  • the carbon nanotube dispersion evaluated as suitable in step (A-iii) or (A-v) may be used as it is, or may be adjusted to the fractal dimension and/or CNT persistence length defined in step (A-iii). Further dispersion processing may be performed within the range that satisfies the conditions before use.
  • the method for producing a carbon nanotube dispersion of the present invention comprises the following steps: (B1-i) a step of dispersing a mixture of single-walled carbon nanotubes having a G/D ratio of 5 or less and a solvent to obtain a carbon nanotube dispersion; (B1-ii) obtaining an image by imaging the carbon nanotube dispersion at a concentration of 0.1 wt% for the obtained carbon nanotube dispersion; (B1-iii) If the condition 3 that the area ratio of the carbon nanotubes in the acquired image is 55% or less is satisfied, the carbon nanotube dispersion is evaluated as appropriate, and if the condition 3 is not satisfied , evaluating the carbon nanotube dispersion as unsuitable.
  • the secondary battery electrode can exhibit a strong peel strength between the electrode mixture layer and the current collector composed of a metal or the like, and the electrode mixture layer with the peeling base material can be used. It is possible to obtain a carbon nanotube dispersion that can exhibit weak peel strength between the material layer and the release base material composed of resin or the like, and that can exhibit excellent rate characteristics in the secondary battery.
  • the condition may further include the condition that 5 or more and 100 or less carbon nanotubes having an aspect ratio of 10 or more are included per area corresponding to 26000 ⁇ m 2 in the image. That is, in the step (B1-iii), the area ratio of carbon nanotubes in the acquired image is 55% or less, and carbon nanotubes having an aspect ratio of 10 or more per area corresponding to 26000 ⁇ m 2 in the image.
  • the carbon nanotube dispersion is evaluated as appropriate, and if the condition 4 is not satisfied, the carbon nanotube dispersion is not appropriate. It is preferably done by evaluation.
  • this manufacturing method by further adding a condition that 5 or more and 100 or less carbon nanotubes having an aspect ratio of 10 or more are included per area corresponding to 26000 ⁇ m 2 in the image, It is possible to further demonstrate the strong peel strength between the electrode mixture layer and the current collector made of metal, etc., and the electrode mixture layer with the release base material is composed of the electrode mixture layer and resin, etc. It is possible to obtain a carbon nanotube dispersion liquid that can further exhibit weak peel strength between itself and the peeling substrate, and further exhibit excellent rate characteristics for secondary batteries.
  • the method for producing a carbon nanotube dispersion of the present invention comprises the following steps: (B2-i) a step of dispersing a mixture of single-walled carbon nanotubes having a G/D ratio of 10 or more and a solvent to obtain a carbon nanotube dispersion; (B2-ii) obtaining an image by imaging the carbon nanotube dispersion at a concentration of 0.1 wt% for the obtained carbon nanotube dispersion; (B2-iii) If the condition 5 that the area ratio of the carbon nanotubes in the acquired image is 75% or more is satisfied, the carbon nanotube dispersion is evaluated as appropriate, and if the condition 5 is not satisfied , evaluating the carbon nanotube dispersion as unsuitable.
  • the area ratio of the carbon nanotubes measured above is 75% or more.
  • the secondary battery electrode can exhibit a strong peel strength between the electrode mixture layer and the current collector composed of metal or the like, and the electrode mixture layer with the peeling base material can exhibit a strong peel strength. It is possible to obtain a carbon nanotube dispersion that can exhibit weak peel strength between the material layer and the release base material composed of resin or the like, and that can exhibit excellent rate characteristics in the secondary battery.
  • the method for producing a carbon nanotube dispersion of the present invention may further comprise the following steps: (B-iv) further dispersing the carbon nanotube dispersion when the carbon nanotube dispersion is evaluated as inappropriate; (Bv) Steps (B1-ii) and (B1-iii) in the case of embodiment B1, or steps (B2-ii) and (B2-iii) in the case of embodiment B2 are repeated to disperse the carbon nanotubes assessing whether the fluid is adequate; (B-vi) Optionally repeating steps (B-iv) and (Bv).
  • the carbon nanotubes used in the method for producing a carbon nanotube dispersion of the present invention, the solvent, and the various content ratios in the mixture subjected to the dispersion treatment are the same as those described above. can be used. Further, the details of the distributed processing in steps (B1-i), (B2-i), and (B-iv) are as described above. Further details of image acquisition and image analysis from carbon nanotube dispersions are described above.
  • the carbon nanotube dispersion evaluated as appropriate in step (B1-iii), (B2-iii), or (Bv) may be used as it is, or may be subjected to step (B1-iii) or (B2-iii). ) and/or the number of carbon nanotubes having an aspect ratio within a predetermined range, the carbon nanotubes may be further dispersed before use.
  • the method for producing the carbon nanotube dispersion of the present invention comprises the following steps: (i) dispersing a mixture of carbon nanotubes and a solvent to obtain a carbon nanotube dispersion; (ii) acquiring an image by imaging the obtained carbon nanotube dispersion; (iii) If the area ratio of the carbon nanotubes in the acquired image satisfies the condition A, the carbon nanotube dispersion is evaluated as appropriate, and if the condition A is not satisfied, the carbon nanotube dispersion is appropriate. The process of evaluating otherwise.
  • condition A includes that the area ratio of carbon nanotubes is 70% or less.
  • the use of the CNT dispersion liquid obtained by this production method makes it possible to achieve good film-forming properties when forming a carbon film.
  • the above method for producing a carbon nanotube dispersion liquid can be applied to carbon having a porosity within a desired range. It can be used for the production of membranes.
  • the condition A to the condition that the area ratio of the carbon nanotubes in the acquired image is 20% or more and 70% or less, preferably 55% or more and 70% or less, the carbon nanotubes useful for battery applications, for example, 60% It is possible to obtain a CNT dispersion capable of obtaining a carbon film having a high porosity of 99% or less.
  • the method for producing the carbon nanotube dispersion of the present invention may further include the following steps: (iv) further dispersing the carbon nanotube dispersion when the carbon nanotube dispersion is evaluated as inappropriate; (v) repeating steps (ii) and (iii) to assess whether the carbon nanotube dispersion is correct; (vi) repeating steps (iv) and (v);
  • the carbon nanotubes used in the method for producing a carbon nanotube dispersion of the present invention, the solvent, and the various content ratios in the mixture subjected to the dispersion treatment are the same as those described above. can be used. Further, the details of the distributed processing of steps (i) and (iv) are as described above. Furthermore, the details of the area ratio measurement in step (iii) are as described above.
  • the carbon nanotube dispersion evaluated to be appropriate in step (iii) or (v) may be used as it is, or may be further subjected to a dispersion treatment within a range that satisfies the area ratio conditions specified in step (iii). may be used.
  • the method for producing the carbon nanotube dispersions of embodiments B1, B2, and C comprises: a step of measuring the obtained carbon nanotube dispersion by an ultra-small angle X-ray scattering method;
  • the fractal dimension in the wave number range of 0.001 (1/ ⁇ ) or more and 0.3 (1/ ⁇ ) or less when analyzing the scattering curve obtained by measurement by the ultra-small angle X-ray scattering method with the Beaucage model is 3 or more
  • this manufacturing method under the condition that the fractal dimension measured above is in the range of 3 or more and 4 or less, there is a It is possible to exhibit a strong peel strength of the peeling base material layer, and the weak peel strength between the electrode mixture layer and the peeling base material composed of resin etc. can be exhibited. It is possible
  • the method for producing the carbon nanotube dispersions of embodiments B1, B2, and C comprises: 0.001 (1/ ⁇ ) in the wavenumber range of 0.3 (1/ ⁇ ) or more, the fractal dimension is 3 or more and 4 or less, and the wavenumber range of 0.05 (1/ ⁇ ) or more and 0.01 (1/ ⁇ ) or less a step of evaluating the carbon nanotube dispersion as being appropriate when the condition 2 in which the CNT persistence length is in the range of 100 nm or more is satisfied, and evaluating the carbon nanotube dispersion as being inappropriate when the condition 2 is not satisfied; , is preferably further included.
  • the electrode mixture layer and the current collector composed of metal or the like are added to the secondary battery electrode. It is possible to further exhibit strong peel strength between the layers, and to further exhibit weak peel strength between the electrode mixture layer and the release substrate composed of a resin or the like in the electrode mixture layer with the release substrate. It is possible to obtain a carbon nanotube dispersion that can further exhibit excellent rate characteristics in secondary batteries, or that can achieve good film-forming properties when forming a bare film.
  • the method for producing the carbon nanotube dispersion of the present invention may further include the following steps: ( ⁇ ) a step of measuring the obtained carbon nanotube dispersion by an ultra-small angle X-ray scattering method; ( ⁇ ) a fractal dimension of 3 or more and 4 or less in the wave number range of 0.001 to 0.3 (1/ ⁇ ) when analyzing a scattering curve obtained by measuring by an ultra-small angle X-ray scattering method using a Beaucage model; The carbon nanotube dispersion is evaluated as appropriate when the condition 1 in the range is satisfied, and A step of evaluating that the carbon nanotube dispersion liquid is not appropriate when the condition 1 is not satisfied.
  • the fractal dimension measured above is in the range of 3 or more and 4 or less, there is a It is possible to exhibit a strong peel strength of the peeling base material layer, and the weak peel strength between the electrode mixture layer and the peeling base material composed of resin or the like can be exhibited. It is possible to obtain a carbon nanotube dispersion that enables a battery to exhibit excellent rate characteristics or achieves good film-forming properties during the formation of a bare film.
  • the proper evaluation condition for the step ( ⁇ ) is that the CNT persistence length in the wavenumber range of 0.05 to 0.01 (1/ ⁇ ) is 100 nm or more. Further conditions may be included. That is, in the step ( ⁇ ), the fractal dimension in the wave number range of 0.001 to 0.3 (1/ ⁇ ) when analyzing the scattering curve obtained by the ultra-small angle X-ray scattering method using the Beaucage model is The carbon nanotube dispersion is appropriate when condition 2 is satisfied, in which the range is 3 or more and 4 or less, and the CNT persistence length in the wavenumber range of 0.05 to 0.01 (1/ ⁇ ) is in the range of 100 nm or more.
  • the carbon nanotube dispersion is evaluated as being inappropriate when the condition 2 is not satisfied.
  • the secondary battery electrode by further adding the condition that the CNT persistence length measured above is 100 nm or more, the secondary battery electrode has an electrode mixture layer and a current collector composed of metal or the like. It is possible to further exhibit strong peel strength between the layers, and to further exhibit weak peel strength between the electrode mixture layer and the release substrate composed of a resin or the like in the electrode mixture layer with the release substrate. It is possible to obtain a carbon nanotube dispersion that can further exhibit excellent rate characteristics in secondary batteries, or that can achieve good film-forming properties when forming a bare film.
  • the method for evaluating the carbon nanotube dispersion comprises the following steps: (a) measuring the obtained carbon nanotube dispersion by ultra-small angle X-ray scattering; (b) fractal dimension of 3 or more and 4 or less in the wave number range of 0.001 to 0.3 (1/ ⁇ ) when analyzing the scattering curve obtained by measuring by the ultra-small angle X-ray scattering method with the Beaucage model Evaluate the carbon nanotube dispersion as appropriate when satisfying condition 1 in the range, and A step of evaluating that the carbon nanotube dispersion liquid is not appropriate when the condition 1 is not satisfied.
  • the fractal dimension measured above is in the range of 3 or more and 4 or less, there is a It is possible to exhibit a strong peel strength of the peeling base material layer, and the weak peel strength between the electrode mixture layer and the peeling base material composed of resin or the like can be exhibited.
  • a carbon nanotube dispersion can be screened that allows the battery to exhibit excellent rate characteristics.
  • the proper evaluation condition of the step (b) may further include the condition that the CNT persistence length in the wavenumber range of 0.05 to 0.01 (1/ ⁇ ) is 100 nm or more. good. That is, in the step (b), the fractal dimension in the wavenumber range of 0.001 to 0.3 (1/ ⁇ ) when analyzing the scattering curve obtained by the ultra-small angle X-ray scattering method using the Beaucage model is The carbon nanotube dispersion is appropriate when condition 2 is satisfied, in which the range is 3 or more and 4 or less, and the CNT persistence length in the wavenumber range of 0.05 to 0.01 (1/ ⁇ ) is in the range of 100 nm or more.
  • the carbon nanotube dispersion may be evaluated as inappropriate.
  • this evaluation method by further adding the condition that the CNT persistence length measured above is 100 nm or more, the electrode mixture layer and the current collector composed of metal or the like are added to the secondary battery electrode. It is possible to further exhibit strong peel strength between the layers, and to further exhibit weak peel strength between the electrode mixture layer and the release substrate composed of a resin or the like in the electrode mixture layer with the release substrate. It is possible to select a carbon nanotube dispersion liquid that can further exhibit excellent rate characteristics in secondary batteries.
  • step (b) The details of the ultra-small angle X-ray scattering measurement in step (b) are as described above.
  • the method for evaluating a carbon nanotube dispersion is used to evaluate a carbon nanotube dispersion containing single-walled carbon nanotubes having a G/D ratio of 5 or less and a solvent, and includes the following steps: (a) obtaining an image by imaging the obtained carbon nanotube dispersion at a concentration of 0.1 wt%; (B) If the condition 1 is satisfied that the area ratio of the carbon nanotubes in the acquired image is 55% or less, the carbon nanotube dispersion is evaluated as appropriate, and if the condition 1 is not satisfied, the carbon Evaluating the nanotube dispersion as unsatisfactory.
  • the area ratio of the carbon nanotubes measured above is 55% or less.
  • the secondary battery electrode can exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal etc. It is possible to select a carbon nanotube dispersion liquid that can exhibit weak peel strength between the base material and the release base material composed of resin or the like and that can exhibit excellent rate characteristics in the secondary battery.
  • the appropriate evaluation condition of the step (b) is that 5 or more and 100 or less carbon nanotubes with an aspect ratio of 10 or more are included per area corresponding to 26000 ⁇ m 2 in the image.
  • the method for evaluating a carbon nanotube dispersion is used to evaluate a carbon nanotube dispersion containing single-walled carbon nanotubes having a G/D ratio of 10 or more and a solvent, and includes the following steps: (a) obtaining an image by imaging the obtained carbon nanotube dispersion at a concentration of 0.1 wt%; (b) If the condition 3 is satisfied that the area ratio of the carbon nanotubes in the acquired image is 75% or more, the carbon nanotube dispersion is evaluated as appropriate, and if the condition 3 is not satisfied, the carbon Evaluating the nanotube dispersion as unsatisfactory.
  • the area ratio of the carbon nanotubes measured above is said to be 75% or more.
  • the secondary battery electrode can exhibit strong peel strength between the electrode mixture layer and the current collector composed of metal etc. It is possible to select a carbon nanotube dispersion liquid that can exhibit weak peel strength between the base material and the release base material composed of resin or the like and that can exhibit excellent rate characteristics in the secondary battery.
  • the method for evaluating the carbon nanotube dispersion comprises the following steps: (a) acquiring an image by imaging the carbon nanotube dispersion; (b) If the area ratio of the carbon nanotubes in the acquired image satisfies the condition A, the carbon nanotube dispersion is evaluated as appropriate, and if the condition A is not satisfied, the carbon nanotube dispersion is appropriate. The process of evaluating otherwise.
  • condition A includes that the area ratio of carbon nanotubes is 70% or less.
  • a carbon nanotube dispersion evaluated as appropriate by this evaluation method can be used for forming a carbon film.
  • the CNT dispersion selected by this evaluation method is used under the condition that the area ratio of the carbon nanotubes measured above is 70% or less, good film-forming properties can be obtained when forming a carbon film. is achievable.
  • the details of the area ratio measurement in step (b) are as described above.
  • condition A is a condition that the area ratio of the carbon nanotubes in the acquired image is 20% or more and 70% or less, preferably 55% or more and 70% or less.
  • Using a CNT dispersion makes it possible to obtain a carbon film having a high porosity of, for example, 60% or more and 99% or less.
  • a high porosity of, for example, 60% or more and 99% or less can be achieved by using a carbon nanotube dispersion selected by this evaluation method.
  • the correlation between the area ratio of the CNT dispersion and the porosity of the obtained carbon film is as described above.
  • the method for evaluating the carbon nanotube dispersion of Aspect A may be combined with the method for evaluating the carbon nanotube dispersion of any one of Aspects B1, B2, and C.
  • the present invention also provides a method of manufacturing a carbon film.
  • the method for producing a carbon film of the present invention includes the step of forming a carbon film by removing the solvent from the above-described CNT dispersion having a CNT area ratio of 70% or less. According to this manufacturing method, by using a CNT dispersion having a CNT area ratio of 70% or less, it is possible to manufacture a carbon film with good film-forming properties.
  • the porosity in the desired range can be obtained. It becomes possible to obtain a carbon film having For example, if a CNT dispersion having an area ratio measured above of 20% or more and 70% or less, preferably 55% or more and 70% or less, is used, a carbon film having a high porosity of, for example, 60% or more and 99% or less can be obtained. Obtainable.
  • the correlation between the area ratio of the CNT dispersion and the porosity of the obtained carbon film is as described above.
  • the carbon film production method of the present invention is obtained by removing the solvent from the CNT dispersion obtained by the above-described CNT dispersion production method and sorted under the condition that the CNT area ratio is 70% or less. , including the step of forming a carbon film. According to this manufacturing method, by using a CNT dispersion selected under the condition that the CNT area ratio is 70% or less, it is possible to manufacture a carbon film with good film-forming properties.
  • a CNT dispersion selected under conditions in which the area ratio of CNTs in an image obtained by imaging the CNT dispersion is within a predetermined range is used as the CNT dispersion, desired It becomes possible to obtain a carbon film having a porosity in the range of For example, if a CNT dispersion selected under the condition that the area ratio measured above is 20% or more and 70% or less, preferably 55% or more and 70% or less, a high porosity of 60% or more and 99% or less can be obtained. can be obtained.
  • the correlation between the area ratio of the CNT dispersion and the porosity of the obtained carbon film is as described above.
  • the step of removing the solvent from the CNT dispersion to form a carbon film can be performed using, for example, any one of the following methods (A) and (B).
  • the carbon films obtained by the above methods (A) and (B) correspond to those obtained by peeling off the above-described dried product from the growth substrate.
  • a porous structure having a highly developed network can be obtained by forming a film using a CNT dispersion having a CNT area ratio of 70% or less. It is presumed that a possible carbon film can be obtained.
  • the film-forming substrate is not particularly limited, and known substrates can be used according to the application of the carbon film to be produced.
  • examples of film-forming substrates to which the CNT dispersion is applied in method (A) include resin substrates, glass substrates, and metal substrates.
  • the resin base material polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), polyimide, polyphenylene sulfide, aramid, polypropylene, polyethylene, polylactic acid, polyvinyl chloride, polycarbonate, Substrates made of polymethyl methacrylate, alicyclic acrylic resins, cycloolefin resins, triacetyl cellulose and the like can be mentioned. Further, as the glass substrate, a substrate made of ordinary soda glass can be mentioned. Examples of metal substrates include substrates made of aluminum, copper, or the like.
  • Examples of the film-forming substrate for filtering the CNT dispersion in the above method (B) include filter paper and porous sheets made of cellulose, nitrocellulose, alumina, resin, or the like.
  • a membrane filter can be used as the film-forming base material.
  • the coating method includes a dipping method, a roll coating method, a gravure coating method, a knife coating method, an air knife coating method, a roll knife coating method, a die coating method, a screen printing method, a spray coating method, a gravure offset method, and the like. can be used.
  • a known filtration method can be employed as a method for filtering the CNT dispersion liquid using the film-forming substrate in the above method (B). Specifically, natural filtration, vacuum filtration, pressure filtration, centrifugal filtration, etc. can be used as the filtration method.
  • drying As a method for drying the CNT dispersion applied on the film-forming substrate in the above method (A) or the filtrate obtained in the above method (B), a known drying method can be employed. Examples of the drying method include hot air drying, vacuum drying, hot roll drying, and infrared irradiation.
  • the drying temperature is not particularly limited, but usually room temperature to 200° C.
  • the drying time is not particularly limited, but is usually 0.1 to 150 minutes.
  • the carbon film formed in the film formation step may be washed.
  • the cleaning of the carbon film can be performed by washing away impurities remaining in the carbon film with a solvent.
  • the solvent used for washing is not particularly limited, and the above-described solvent that can be used as the solvent for the CNT dispersion, preferably the same solvent as the solvent for the CNT dispersion can be used.
  • the contact between the carbon film and the solvent can be carried out by immersing the carbon film in the solvent or applying the solvent to the carbon film. Additionally, the carbon film after washing can be dried using known methods.
  • the carbon film formed in the film formation step may be pressed to further increase the density.
  • the press pressure during press working is preferably less than 3 MPa, and more preferably not press work.
  • the carbon film obtained by the method for producing a carbon film of the present invention contains CNTs contained in the above-described CNT dispersion having an area ratio of 70% or less. Since the above carbon film contains CNTs contained in a CNT dispersion having a CNT area ratio of 70% or less, it is formed in a favorable state and becomes a self-supporting carbon film with high conductivity and porosity.
  • the carbon film preferably contains CNTs contained in a CNT dispersion having a CNT area ratio within a predetermined range, whereby the carbon film has a porosity within a desired range.
  • the carbon film can have a high porosity, for example ⁇ 60% and ⁇ 99%.
  • the correlation between the area ratio of the CNT dispersion and the porosity of the obtained carbon film is as described above.
  • the carbon film obtained by the method for producing a carbon film of the present invention is, for example, a conductive sheet (e.g., It can be used as a conductive film for solar cells, touch panels, etc.), a heat conductive sheet, an electromagnetic wave absorbing sheet, a battery sheet, and the like.
  • a conductive sheet e.g., It can be used as a conductive film for solar cells, touch panels, etc.
  • a heat conductive sheet e.g., an electromagnetic wave absorbing sheet
  • a battery sheet e.g., and the like.
  • FT-IR ⁇ Fourier transform infrared spectroscopy
  • CNT aggregate ⁇ Creation of pore distribution curve (CNT aggregate)>
  • the adsorption isotherm was measured using BELSORP-miniII (manufactured by Microtrack Bell) at 77 K using liquid nitrogen (adsorption equilibrium time was 500 seconds).
  • vacuum degassing was performed at 100° C. for 12 hours.
  • the pore distribution curve of each sample was obtained from the adsorption amount of this adsorption isotherm by the BJH method.
  • the measurement range of the pore diameter was 1 nm or more and less than 400 nm.
  • FIG. 5 is one of ten images obtained for the above CNT aggregate.
  • a test sample was obtained by placing the prepared dispersion in a measurement capillary. Then, the obtained test sample was subjected to ultra-small angle X-ray scattering measurement under the following conditions to obtain a scattering image.
  • Table 1 shows the values of the fractal dimension P 3 and the persistence length R g,2 of the CNT.
  • ⁇ G/D ratio of CNT> A Raman spectrum of CNT was measured using a microlaser Raman spectrophotometer (Nicolet Almega XR manufactured by Thermo Fisher Scientific Co., Ltd.). Then, the intensity of the G band peak observed near 1590 cm ⁇ 1 and the intensity of the D band peak observed near 1340 cm ⁇ 1 were determined for the obtained Raman spectrum, and the G/D ratio was calculated.
  • ⁇ Area ratio of CNT (jet mill CNT dispersion)> A CNT dispersion prepared by a jet mill was adjusted to a concentration of 0.1 wt % with a solvent (the same solvent used for the CNT dispersion), and 1 ⁇ L of each was dropped onto five spots on a slide glass. The dropped CNT dispersion was observed using a digital microscope (manufactured by Keyence Corporation, product name “VHX-900”) at a magnification of 500 to obtain an image.
  • FIG. 7 shows an example of an image obtained by a digital microscope from the CNT dispersion.
  • FIG. 8 shows the image after the binarization process.
  • ⁇ Number of CNTs with an aspect ratio within a predetermined range> Using the binarized image obtained above, the diameter and length of all carbon nanotubes in the area corresponding to 26000 ⁇ m 2 of the binarized image are measured and the aspect ratio (ratio of diameter to length. length/diameter) was calculated, and the number of CNTs having an aspect ratio within a predetermined range was obtained.
  • ⁇ Area ratio of CNT (high-shear stirring CNT dispersion)> A CNT dispersion prepared by high-shear stirring was adjusted to a concentration of 0.1 wt% with a solvent (the same solvent used for the CNT dispersion), and 10 ⁇ L of the concentration-adjusted CNT dispersion was placed on a slide glass at a thickness of 20 mm. An area of 50 mm ⁇ 50 mm was coated, and five spots in the coated area were observed at a magnification of 500 using a digital microscope (manufactured by Keyence Corporation, product name “VHX-7000”) to obtain an image.
  • ⁇ Mechanical strength of positive electrode peel strength of positive electrode mixture layer against current collector> A rectangular test piece having a length of 100 mm and a width of 10 mm was cut from the prepared positive electrode. With the surface of the positive electrode mixture layer facing down, cellophane tape was attached to the surface of the positive electrode mixture layer. At this time, the cellophane tape specified in JIS Z1522 was used. In addition, the cellophane tape was fixed to the test table. After that, the stress when one end of the current collector was pulled vertically upward at a pulling rate of 50 mm/min and peeled off was measured.
  • ⁇ Positive electrode weight> The positive electrodes produced in Examples and Comparative Examples were cut into 5 cm ⁇ 5 cm (area: 25 cm 2 ) to obtain test pieces. Then, the mass W (g) of the test piece was divided by the area of the test piece to calculate the basis weight (g/cm 2 ) of the positive electrode.
  • ⁇ Thickness of positive electrode> The positive electrodes produced in Examples and Comparative Examples were cut into 5 cm ⁇ 5 cm test pieces to obtain test pieces, and the thickness thereof was measured using a “Digimatic standard outer micrometer” manufactured by Mitutoyo Corporation.
  • ⁇ Positive electrode density> The positive electrodes produced in Examples and Comparative Examples were cut into 5 cm ⁇ 5 cm test pieces to obtain test pieces, the thickness of each test piece was measured with a micrometer, and the volume (cm 3 ) of each test piece was calculated. Then, the density (g/cm 3 ) of the positive electrode was calculated by dividing the mass W (g) of the test piece, which was calculated in the same manner as in the above ⁇ positive electrode basis weight>, by the volume (cm 3 ) of the test piece.
  • Electrode conductivity 1 of positive electrode mixture layer The electrical conductivity 1 of the positive electrode mixture layer on the positive electrode produced in Examples and Comparative Examples was measured using a resistivity meter for low resistance ("Loresta (registered trademark) GX" manufactured by Mitsubishi Chemical Analytic). According to JIS K 7194:1994, the electrical conductivity 1 was calculated by performing a four-probe method by arranging probes on one side of the sheet.
  • Electrode conductivity 2 of positive electrode mixture layer The electrical conductivity 2 of the positive electrode mixture layer on the positive electrode produced in Examples and Comparative Examples was measured using a resistivity meter for low resistance (manufactured by Mitsubishi Chemical Analytic, "Loresta (registered trademark) GX"). According to JIS K 7194:1994, electric conductivity 2 was calculated by performing a four-probe method in which probes are arranged on one side of the sheet.
  • the above operation and measurement were repeated 5 times, and the average value of the amount of falling powder from the electrodes of 5 specimens was obtained. Then, the powder drop resistance of the electrode mixture layer was evaluated according to the following criteria. The smaller the amount of powder falling from the electrode, the more excellent the powder falling resistance of the electrode mixture layer.
  • ⁇ Porosity> The porosity of the produced carbon film was measured by a mercury intrusion method (manufactured by Shimadzu Corporation, Autopore IV9510).
  • FIG. 7 shows a schematic configuration of a CNT aggregate manufacturing apparatus 200 used.
  • a CNT aggregate manufacturing apparatus 200 shown in FIG. 204 and a gas mixture prevention device 203 for preventing gas from mixing between the formation unit 202 and the growth unit 204 .
  • the CNT aggregate manufacturing apparatus 200 includes an inlet purge device 201 arranged in the front stage of the formation unit 202, an outlet purge device 205 arranged in the rear stage of the growth unit 204, and further arranged in the rear stage of the outlet purge device 205.
  • the cooling unit 206 and other components are provided.
  • the formation unit 202 includes a formation furnace 202a for holding the reducing gas, a reducing gas injection device 202b for injecting the reducing gas, a heating device 202c for heating at least one of the catalyst and the reducing gas, and the gas in the furnace. It is composed of an exhaust device 202d and the like for discharging to the outside of the system.
  • the gas mixture prevention device 203 includes an exhaust device 203a and a purge gas injection device 203b that injects a purge gas (seal gas).
  • the growth unit 204 includes a growth furnace 204a for maintaining the source gas environment, a source gas injection device 204b for injecting the source gas, a heating device 204c for heating at least one of the catalyst and the source gas, An exhaust device 204d or the like for discharging gas to the outside of the system is provided.
  • An inlet purge device 201 is attached to a connecting portion 209 that connects an antechamber 213, which is a component for introducing a substrate 211 into the system via a hopper 212, and a formation furnace 202a.
  • the cooling unit 206 includes a cooling container 206a for holding inert gas, and a water cooling device 206b arranged to surround the space inside the cooling container 206a.
  • the transport unit 207 is a unit that continuously transports the substrate 211 by screw rotation. It is implemented by a screw vane 207a and a driving device 207b capable of rotating the screw vane to a state in which the substrate can be conveyed.
  • the heating device 214 is configured to be able to heat the inside of the system at a temperature lower than the heating temperature in the formation unit, and heats the vicinity of the driving device 207b.
  • ⁇ catalyst layer forming step>> Zirconia (zirconium dioxide) beads (ZrO 2 , volume average particle diameter D50: 650 ⁇ m) as a substrate are put into a rotating drum type coating device, and while stirring the zirconia beads (20 rpm), an aluminum-containing solution is sprayed through a spray gun. While spraying (spray amount 3 g / min, spray time 940 seconds, spray air pressure 10 MPa), dry while supplying compressed air (300 L / min) into the rotating drum to form an aluminum-containing coating film on the zirconia beads. did. Next, a calcination treatment was performed at 480° C. for 45 minutes to produce primary catalyst particles having an aluminum oxide layer formed thereon.
  • the primary catalyst particles were put into another rotary drum type coating device and stirred (20 rpm) while the iron catalyst solution was sprayed with a spray gun (spray amount: 2 g/min, spray time: 480 seconds, spray air pressure: 5 MPa). ) and dried while supplying compressed air (300 L/min) into the rotating drum to form an iron-containing coating film on the primary catalyst particles.
  • a sintering treatment was performed at 220° C. for 20 minutes to produce a substrate on which an iron oxide layer was further formed.
  • ⁇ CNT synthesis process>> The base material having a catalyst on its surface prepared in this way was put into the feeder hopper of the manufacturing apparatus, and while being conveyed by the screw conveyor, the formation process, the growth process, and the cooling process were performed in order to manufacture a CNT aggregate. .
  • the characteristics of the produced CNT aggregate are, as typical values, G/D ratio: 1.3, tapped bulk density: 0.02 g/cm 3 , average CNT length: 150 ⁇ m, BET specific surface area: 900 m 2 /g, The average outer diameter was 4.0 nm and the carbon purity was 99%.
  • ⁇ Production of positive electrode slurry composition 100.0 parts of LiNi 0.5 Co 0.3 Mn 0.2 O 2 (NCM532) as a positive electrode active material, 0.1 part of a CNT dispersion as a conductive material dispersion, and polyvinylpyrrolidone as a binder 0.2 parts of, 1.0 parts of hydrogenated NBR as a dispersant, and 50 parts of NMP as a slurry composition solvent are stirred in a planetary mixer to obtain a positive electrode slurry composition. manufactured.
  • NCM532 LiNi 0.5 Co 0.3 Mn 0.2 O 2
  • the positive electrode slurry composition obtained above was applied to the surface of a current collector made of an aluminum foil having a thickness of 20 ⁇ m and a surface tension of 900 mN/m using a comma coater, and dried at 60° C. for 20 minutes. After that, heat treatment was performed at 150° C. for 1 hour to obtain a positive electrode original sheet. Then, by rolling the obtained positive electrode raw material with a roll press, a current collector (metal film) and a positive electrode mixture layer (carbon nanotube-containing film) formed on the current collector are provided, and the thickness is A positive electrode (laminate) was manufactured in which the thickness was controlled to 50 ⁇ m.
  • the positive electrode slurry composition obtained above was applied to the surface of a transfer release substrate made of a polypropylene resin substrate having a thickness of 20 ⁇ m and a surface tension of 30 mN/m. and then heat-treated at 150° C. for 1 hour to obtain a laminate material for current collector transfer. Then, by rolling the obtained laminate raw material for current collector transfer with a roll press, a release base material (resin base material) and a positive electrode mixture layer (containing carbon nanotubes) formed on the release base material film) and the thickness was controlled to 50 ⁇ m to produce a laminate for current collector transfer.
  • a transfer release substrate made of a polypropylene resin substrate having a thickness of 20 ⁇ m and a surface tension of 30 mN/m.
  • the positive electrode for a lithium ion secondary battery obtained above was cut into a disk shape with a diameter of 16 mm.
  • a separator polypropylene porous film, disk shape, diameter 18 mm, thickness 25 ⁇ m
  • a negative electrode metallic lithium, disk shape, diameter 18 mm, thickness 0.5 mm
  • the obtained laminate was placed in a stainless steel coin-shaped outer container (20 mm in diameter, 1.8 mm in height, 0.25 mm in thickness of stainless steel) equipped with a polypropylene packing.
  • the electrolytic solution was poured into the container so that no air remained, and the outer container was covered with a stainless steel cap having a thickness of 0.2 mm via a polypropylene packing and fixed to seal the battery can.
  • Example 2 In the production of the CNT dispersion, Tuball (trademark), which is a single-walled carbon nanotube (manufactured by OCSiAl, Inc., CNT diameter: 1.6 ⁇ 0.4 nm, specific surface area ⁇ 300 m / g, G / D ratio: > 90 , length: 5 ⁇ m), in the same manner as in Example 1, production of a CNT dispersion liquid and measurement of each physical property value, production of a carbon film and evaluation of each performance were performed. The G/D ratio of CNT was 90. Results are shown in Tables 1 and 2. An optical microscope image and a binarized image of the CNT dispersion are shown in FIGS. 2 and 11, respectively. A photograph of grindometer analysis of the slurry composition and a photograph of the positive electrode are shown in FIG. Grindometer analysis exceeded the 40 ⁇ m line, confirming that there were no aggregates or particles in the dispersion and that the degree of dispersion was good.
  • Example 3 In the production of the CNT dispersion, 9 parts of CNT_A and 1 part of CNT obtained by the super-growth method (product name “ZEONANO SG101”, manufactured by Nippon Zeon Co., Ltd.) were used as the CNTs. (same as CNTs) was used, in the same manner as in Example 1, production of a CNT dispersion liquid and measurement of each physical property value, production of a carbon film and evaluation of each performance were performed. The G/D ratio of the CNT mixture was 1.2. Results are shown in Tables 1 and 2. An optical microscope image and a binarized image of the CNT dispersion are shown in FIGS. 3 and 12 (solid lines indicate carbon nanotubes with an aspect ratio of 10 or more), respectively. A photograph of grindometer analysis of the slurry composition and a photograph of the positive electrode are shown in FIG. Grindometer analysis exceeded the 40 ⁇ m line, confirming that there were no aggregates or particles in the dispersion and that the degree of dispersion was good.
  • Example 2 Except for using the product name "K-nanos 100T" (manufactured by KNANO GRAPHENE COMPANY, CNT diameter: 7 to 23 nm, CNT length: 26 nm, carbon purity: ⁇ 95%) as CNTs in the production of the CNT dispersion, In the same manner as in Example 1, a CNT dispersion was produced and each physical property value was measured, and a carbon film was produced and each performance was evaluated. In addition, the G/D ratio of CNT was 0.9. Table 1 shows the results. FIG. 14 shows an image obtained by binarizing the optical microscope image of the CNT dispersion.
  • Example 5 In the preparation of the CNT dispersion, a CNT dispersion and a carbon film were prepared in the same manner as in Example 4, except that the dispersion treatment was performed under the conditions of condition B shown in Table 3, and each physical property was measured or made an evaluation. Table 4 shows the results.
  • Example 6 ⁇ Synthesis of CNT_A>
  • the CNTs used in Examples 6 and 7 (hereinafter referred to as "CNT_A") were produced in the same manner as in Example 1.
  • Example 7 In the preparation of the CNT dispersion, a CNT dispersion and a carbon film were prepared in the same manner as in Example 6, except that the dispersion treatment was performed under the conditions of condition B shown in Table 3, and each physical property was measured or made an evaluation. Table 4 shows the results.
  • Example 3 In the preparation of the CNT dispersion, a CNT dispersion and a carbon film were prepared in the same manner as in Example 4, except that the product name "K-nanos 100T" (manufactured by KNANO GRAPHENE COMPANY) was used as the CNT. Physical properties were measured or evaluated. Table 4 shows the results.
  • Comparative Example 4 In the preparation of the CNT dispersion, a CNT dispersion and a carbon film were prepared in the same manner as in Comparative Example 3, except that the dispersion treatment was performed under the conditions of condition B shown in Table 3, and the physical properties were measured or made an evaluation. Table 4 shows the results.
  • Table 4 shows that in the cases of Examples 4 to 7 belonging to the scope of the present invention, carbon films were produced with good film-forming properties. Moreover, the results of Examples 4 to 7 showed that adjusting the area ratio of CNTs in the CNT dispersion can serve as a guideline for obtaining a carbon film having a porosity within a desired range.
  • the secondary battery electrode can exhibit a strong peel strength between the electrode mixture layer and the current collector composed of a metal or the like, and the electrode mixture layer with the peeling base material can It is possible to provide a carbon nanotube dispersion liquid that can exhibit weak peel strength between a composite material layer and a release base material composed of a resin or the like and that can exhibit excellent rate characteristics in a secondary battery. can. Further, according to the present invention, it is possible to provide a laminate that can be used as an electrode for a secondary battery, having a strong peel strength between the electrode mixture layer and the current collector made of metal or the like.
  • a laminate that can be used as an electrode mixture layer with a release base material, which has a weak peel strength between the electrode mixture layer and the release base material made of resin or the like. can be done.
  • a CNT dispersion capable of achieving good film-forming properties when forming a carbon film using the CNT dispersion, and a method for producing the same.
  • a method for producing a carbon film with good film-forming properties using a CNT dispersion, and a carbon film with a good film-forming state can be done.

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Abstract

Le but de la présente invention est de fournir une dispersion liquide de nanotubes de carbone qui permet à des électrodes de batterie secondaire de démontrer une forte résistance au pelage entre une couche de mélange d'électrode et un collecteur de courant formé à partir d'un métal, etc, et une résistance au pelage faible pour une couche de mélange d'électrode pourvue d'un substrat de libération constitué d'une résine ou similaire, entre la couche de mélange d'électrode et le substrat de libération ; et de permettre à une batterie secondaire de présenter une performance de vitesse supérieure, ou réalise de bonnes propriétés de formation de film lorsqu'un film de carbone est formé. La dispersion liquide de nanotubes de carbone selon la présente invention contient des nanotubes de carbone et un solvant, lorsqu'une courbe de diffusion obtenue par la mesure effectuée avec une méthode de diffusion de rayons X à ultra-petit angle est analysée par le modèle de Beaucage, la dimension fractale dans une plage de nombres d'onde de 0,001 (1/Å) à 0,3 (1/Å) étant dans la plage de 3 à 4.
PCT/JP2023/006082 2022-02-28 2023-02-20 Dispersion liquide de nanotubes de carbone, stratifié, méthode de production de dispersion liquide de nanotubes de carbone, et méthode de production de film de carbone WO2023162937A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100303874A1 (en) * 2007-12-17 2010-12-02 Pinar Akcora Anisotropic self-assembly of nanoparticles in composites
US20130264524A1 (en) * 2012-04-05 2013-10-10 Kang-Yu LIU Electrode and fabrication method thereof
JP2016054113A (ja) * 2014-09-04 2016-04-14 日本ゼオン株式会社 二次電池電極用複合体の製造方法、二次電池電極用複合体、二次電池用電極および二次電池
WO2021193667A1 (fr) * 2020-03-26 2021-09-30 日本ゼオン株式会社 Élément d'étanchéité au gaz pour dispositifs à hydrogène haute pression et dispositif à hydrogène haute pression

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100303874A1 (en) * 2007-12-17 2010-12-02 Pinar Akcora Anisotropic self-assembly of nanoparticles in composites
US20130264524A1 (en) * 2012-04-05 2013-10-10 Kang-Yu LIU Electrode and fabrication method thereof
JP2016054113A (ja) * 2014-09-04 2016-04-14 日本ゼオン株式会社 二次電池電極用複合体の製造方法、二次電池電極用複合体、二次電池用電極および二次電池
WO2021193667A1 (fr) * 2020-03-26 2021-09-30 日本ゼオン株式会社 Élément d'étanchéité au gaz pour dispositifs à hydrogène haute pression et dispositif à hydrogène haute pression

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